Japan: SIP providers and connecting a number to the PBX

This page continues the general guide to connecting a provider's number to the PBX: that page covers everything that is the same in any country — the two trunk modes, what to ask the operator, what to enter in the form, network and compatibility and checking the connection. Here is the Japanese specifics: why a 03 landline number cannot simply be "added to a cloud PBX", where to get a number instead, and what to enter in the form for each provider.

The data was collected on 10 September 2026 from operator websites and regulator documents; links are in the "Sources" section.

In brief#

• A dedicated PBX is created for Japanese locations. The licence to use numbers (a 電気通信番号使用計画 numbering plan recognised by the Ministry of Internal Affairs and Communications) is required from whoever sells telecom service; the venue only needs a contract with such an operator.
• ⚠️⚠️ The key point: a Japanese landline number lives inside a closed network. 0AB-J numbers (03, 06, 045 and so on) are mostly sold as ひかり電話 by NTT East/West, and that is SIP inside the NGN network, not "SIP over the internet": it requires a フレッツ line on the premises, and since 01.05.2012 any customer equipment must pass NTT's terminal conformance test (適合検査). Our PBX runs in the cloud and cannot register with ひかり電話 at all. That leaves three paths: take a 050 number from a provider that allows the public cloud; take a landline number from a wholesale provider that delivers the trunk over the internet; or keep ひかり電話 in the office and install an SBC gateway there.
• Where to start. Rakuten OpenGate is the only large operator that explicitly permits a connection from a public cloud (numbers are 050 only, registration mode). Cloco / ZivaPhone / Teleworks are one platform under three brands: landline numbers, a trunk over the ordinary internet, registration or IP authorisation to choose from, and published server addresses. Brastel Basix is the choice when nobody at the venue speaks Japanese.
• ⚠️ Signalling rate matters more than price. Rakuten requires the registration to be refreshed exactly every 1800 seconds and allows no more than one outbound call per second per number, otherwise it filters your IP address without notice. An outbound dialling campaign cannot be built on such a trunk.
• ⚠️ Tone dialling. In the known working configurations of Rakuten and Basix the DTMF digits travel inside the audio (inband), while our PBX expects them as separate RFC 2833 packets — test the IVR with a live call.
• ⚠️ Paperwork. A landline number is only issued against an address inside its numbering area, and operators ask for an extract from the Japanese company register. A foreign venue without a Japanese company will not get a landline number; a 050 number is noticeably easier — but emergency 110/119 calls usually do not work from it.

Numbers in Japan#

• Country code — +81, national prefix — 0, international access — 010 (sometimes with a 00XY carrier-selection code in front of it).
• 0AB-J landline numbers — 10 digits including the leading zero (9 significant). The area code has a variable length: 03 Tokyo (the 23 wards plus parts of Mitaka, Chōfu and Komae), 06 Osaka, 045 Yokohama, 044 Kawasaki, 048 Saitama, 052 Nagoya, 011 Sapporo, 022 Sendai, 043 Chiba, 047 Ichikawa and Funabashi, 0422 Musashino, 0466 Fujisawa. Example: 03-1234-5678 domestically = +81 3 1234 5678.
• Mobile numbers — 11 digits, starting with 070, 080 or 090.
• 050 — 11 digits, IP telephony numbers: no geography, emergency calls are usually unavailable, but the provider gets such a number without the quality requirements that apply to 0AB-J. This is the main numbering range of "cloud" operators.
• Service numbers: 0120 and 0800 — free for the caller, 0570 (ナビダイヤル) — paid for the caller, 0990 — premium.
• Emergency services: 110 (police), 119 (fire and ambulance), 118 (coast guard); 104 — directory enquiries.
• How numbers are dialled: inside your own area — the subscriber number only, between areas — 0 + area code + number, abroad — 010 + the number in international format.
• In Lines enter the number exactly as the provider issued it: the PBX matches the last seven digits, so writing it with +81 or with 0 makes no difference. What does matter is that Japanese providers deliver the called number differently, and that decides whether the line is matched:
  • Cloco, ZivaPhone, Teleworks — the number in national format (0312345678), the line is matched normally;
  • Rakuten — the SIP login, but their login is the 050 number without its first three digits, so the last seven digits still match;
  • Brastel Basix — the login, while the called number appears only in a service header; the line cannot be told apart by number (see the Basix section).
• ⚠️ The seven-digit trap. Landline numbers have nine significant digits and the match drops the first one: 03-1234-5678 and 03-9234-5678 both end in 2345678. Do not add landline numbers to one account if they differ only in the first digit of the subscriber part.
• What to send as the outbound caller ID — only a number from the same operator's pool, in the format it accepts (usually the national 0312345678). Details are in "Rules and paperwork".

Who issues a number with a SIP trunk#

Rakuten OpenGate — a 050 number cleared for the public cloud#

A 050 telephony operator (successor to Fusion Communications) that has officially supported connecting a third-party PBX since 2010. The service comes in three steps: the basic "IP電話サービス", the "IP電話 B2BUA" add-on (an intermediary server, 100 JPY per number per month) and "IP電話 B2BUA OpenGate" — the same plus NAT traversal and no tie to an internet provider: its table of permitted access lines states "public cloud — ○" outright, at 200 JPY per number per month. OpenGate is exactly what suits our cloud PBX.

The application is submitted on a paper form (they send it by post); OpenGate requires official company documents — an extract from the Japanese company register. A 050 number costs 500 JPY to issue, then 380 JPY a month for the first one and 100 JPY for each further one. Toll-free 0120 numbers come as a separate service, "フリーボイス". The operator has no landline numbers: its 03/06 service closed on 21.05.2022.

What to enter in the admin panel (Telephony → "Trunks and connections" → Add provider):

What to arrange with the provider: apply specifically for "IP電話 B2BUA OpenGate" and attach the register extract → confirm in writing that the connection comes from a public cloud → obtain the list of issued numbers and the server address → order 0120 as a separate service if needed → hand over the Static IP from the "Server" tab if the operator asks to allowlist it.

Pitfalls ⚠️

• Registration rate. The operator requires the registration to be refreshed exactly every 1800 seconds and, with several numbers, staggered by one second; it filters offenders by IP without warning. Our PBX refreshes the registration using its SIP stack default — agree this point with the operator in writing and contact us before you go live.
• One outbound call per second per number — anything faster the operator may refuse to carry. Mass dialling through this trunk is impossible.
• Tone dialling travels inside the audio. The known working configurations use inband DTMF, while we use RFC 2833. Ask for RFC 2833/4733 and test the IVR with a live call.
• The codec is G.711 μ-law, which suits us; media ports 10000–20000 match ours as well.
• 050 only. You cannot get a landline number from this operator, and emergency 110/119 calls usually do not work from 050 — keep an ordinary mobile phone in the dining room.

Sources: B2BUA OpenGate · FAQ on connecting a PBX · pricing — 10.09.2026.

Cloco, ZivaPhone and Teleworks — landline numbers over the ordinary internet#

Three brands on one platform (the cloudpbx.com and cldpbx.com domains), and this is the most predictable way to get a Japanese landline number for a cloud PBX: the trunk runs over the ordinary internet, no dedicated line is needed, and the connection parameters are published. The platform advertises "one registration, many numbers", lists Asterisk-based PBXs as tested, uses G.711 μ-law as the default codec (others by agreement) and delivers the called number in national format, so our line matching works as intended.

Cloco SIPトランク2#

A product for "connecting a third-party IP PBX to the telephone network" with an official Asterisk setup manual. It states outright: "in addition to registration with a login and password, registration by IP only is supported, selectable during setup". Pricing: a trunk ID together with one channel — 1,500 JPY to connect and 1,500 JPY a month, an extra channel the same, a number — 200 JPY and 200 JPY a month. Two-way porting and the full grid of numbering areas are available.

ZivaPhone#

The same engine under a separate brand: a cloud PBX, dialler and a SIP trunk for your own PBX, IP authorisation without a login, and a higher call rate on request. The operator publishes an "addresses and ports to allow" page: the registration server sip3.cldpbx.com in the 202.234.184.128/25 subnet, signalling on UDP 5060 and UDP 25060, audio on UDP 10000–20000.

Teleworks（株式会社テレワークス）#

The platform's third brand (Shinjuku, Tokyo): "a SIP trunk to the public telephone network for companies that run their own SIP server". One channel takes about 100 KB/s; the default codecs are G.711 μ-law and GSM, others by agreement.

What to arrange with the provider (for all three): choose the authorisation mode, and in IP mode hand over the Static IP from the "Server" tab → order the number of channels you need (that is the number of simultaneous conversations) and the numbers → attach the numbers to the trunk → for 0120, 0800 and 0570 collect from the portal the technical number that arrives instead of the public one → fix G.711 as the codec.

Pitfalls ⚠️

• The Cloco manual dates from 2017; the Asterisk versions it lists are long obsolete. The connection parameters themselves have not changed, but confirm them with support before going live.
• The Cloco service page redirected to a maintenance notice on 10.09.2026 — the facts were cross-checked against the platform's sibling brands and the PDF manual.
• There may be more than one login server. ZivaPhone warns that an account can have several server addresses, while our "SIP host" field takes one: you will have to enter the backup address by hand if the main one stops responding.
• GSM is in the Teleworks default list — our PBX does not accept it; ask them to keep G.711 μ-law or a-law.

Sources: Cloco — SIPトランク2 · IP PBX connection manual (PDF) · ZivaPhone — SIPトランク · ZivaPhone — addresses and ports · Teleworks — SIPトランク — 10.09.2026.

Brastel Basix — the operator you can talk to in English#

An international operator that has served foreigners in Japan for many years: support in English and Portuguese, a rarity on this market. Basix is a cloud PBX with landline numbers 03, 043, 044, 045, 048, 052, 06 and 050 numbers, running over any internet connection; its subsidiary ZIP Telecom is a registered telecom operator whose equipment holds the ministry's top quality class. Its strong point is number porting. There is no minimum contract term, an extra 050 number costs 105 JPY a month, and support is reachable at 050-6860-1000.

The operator publishes no official "connect your own PBX" instructions — it sells its own cloud PBX — but the combination has been in use for years and the parameters are known from published working configurations.

What to arrange with the provider: ask in writing whether connecting a third-party IP PBX is supported (the contract does not say) → order the number of simultaneous calls you need in the web portal → attach the numbers to the trunk → find out which addresses inbound calls arrive from → ask for RFC 2833 tone dialling.

Pitfalls ⚠️

• ⚠️⚠️ The inbound call carries the login, not the number. The called number itself is placed in a service header the PBX does not parse, so line matching by number will not work: the call is accepted as "a call from this provider" and goes into routing as one stream. With several numbers you will not be able to tell them apart by line — see the note on a login instead of a number.
• The registration server and the inbound server are different addresses, while our "SIP host" field takes one: inbound calls may not be recognised as "from this provider". Be sure to test with a live call right after connecting, and contact us if inbound calls do not arrive.
• Drops over UDP. Integrators know the "513 Message Too Large" failure over UDP — it is cured by switching the "Transport" field to TCP.
• Tone dialling inside the audio (inband DTMF) — as with Rakuten, this differs from our RFC 2833.
• The parameters were captured by the community, not issued by the operator — confirm the addresses and ports with support before going live.

Sources: Basix · Basix PACKAGE Q&A — 10.09.2026.

An NTT landline number and the workaround with an on-site gateway#

ひかり電話 オフィスタイプ / オフィスA is the main way to have a landline number in Japan: IP telephony over your own フレッツ 光ネクスト or 光クロス line. The office type supports up to 8 channels and 32 numbers from 1,430 JPY a month; オフィスA goes up to 300 channels and 7,000 numbers.

Technically this is SIP with registration too, but it is not applicable to a cloud PBX: the signalling stays inside the closed NGN network, registration is only possible from the line on the venue's premises, and since 01.05.2012 any customer equipment must pass NTT East's or NTT West's terminal conformance test. That is why there is no "what to enter" table here — there is nothing to enter.

What to do about it:

• keep the number — install an SBC gateway in the office and reach it over a trunk (below);
• port the number to a provider with an internet trunk — Cloco, ZivaPhone, Teleworks, IPS PRO (see "Number porting");
• change the number — take a landline or 050 number from a provider that hands out a trunk right away.

⚠️ One more quirk of the office type: a call from your own number to your own number is rejected as busy.

CC Architect SIP Connect — an anynode gateway in the office#

A ready answer to the country's main obstacle: a certified anynode gateway is installed in the office on the ひかり電話 line, and the cloud PBX reaches it over an ordinary SIP trunk — "the cloud PBX connects directly to the office gateway and uses ひかり電話 as a general-purpose SIP trunk". The gateway itself passed NTT East's and NTT West's certification, so the 適合検査 question is closed by the vendor. The subscription starts from 17,000 JPY a month for 10 channels and includes the gateway, the licence, the connection profile and support; both NTT operators' office type and オフィスA are supported.

What to arrange with the provider: order SIP Connect for "our own Asterisk-based PBX" → hand over the Static IP from the "Server" tab for the gateway's allowlist → agree on G.711 codecs and RFC 2833 tone dialling → settle who maintains the public address of the office gateway → clarify the format of the called number in inbound calls.

Pitfalls ⚠️ A second point of failure appears: if the office internet goes down, telephony goes down with it, even though the PBX in the cloud is alive. The integrator's chart of mutually certified cloud PBXs dates from 2021 — ask whether a ready profile for our PBX exists. The gateway supports TLS encryption, while our trunks only work over UDP and TCP — ask for a profile without TLS.

Sources: NTT East — ひかり電話オフィスタイプ · CC Architect SIP Connect — 10.09.2026.

More providers: parameters come from the account manager#

These companies do offer a trunk for your own PBX, but they publish neither the server address, nor the port, nor the authorisation mode, nor the codecs — everything arrives in the order documents after the contract. Fill in the form from the sheet they send, and take your questions from What to ask the provider.

• IPS PRO / LIPSE (株式会社IPS) — a wholesale trunk "for CTI, cloud PBXs and call centres" over the ordinary internet, with a fully published price list: a channel 1,200 JPY a month, an 03 or 050 number 100 JPY, 0120 2,000 JPY, 0800 1,500 JPY, 0570 10,000 JPY, line connection 10,000–14,000 JPY, number porting 3,000 JPY; billing is per second. Lead time is about two weeks, the phone number is 03-3549-7626. You can choose the underlying carrier — Arcstar IP Voice, KDDI 光ダイレクト or their own network — and the choice determines which ranges are available (0570 only via Arcstar). ⚠️ The seller targets resellers: state plainly in the application that you need one trunk with 2–4 channels.
• CloudNippon — a Tokyo provider (+81 3-6635-9359, info@cloudnippon.com) with a bilingual website: Japanese and foreign numbers, claimed compatibility with Asterisk and FreePBX. According to the 3CX PBX vendor's catalogue, the trunk number is entered in the international +81… format and TLS encryption is not supported — which suits us. ⚠️ Number and minute prices are available on request only.
• Oedo Telecom (大江戸テレコム) — a Tokyo company with a bilingual website: a SIP trunk, their own IP PBX, landline numbers, 0120 and 0570 in one system. ⚠️ Not a single trunk parameter is published; the SLA and channel count are negotiated individually. Ask for "the SIP trunk only", without their IP PBX.
• NTT Com — Arcstar IP Voice — corporate telephony with 0AB-J and 050 numbers. The relevant plan for a cloud PBX is Flexible InterConnect: the operator advertises outbound calls from 050 and 0AB-J numbers "for voice equipment in a public cloud, without laying a physical line". ⚠️ Two extra contracts are required (Arcstar Universal One and Flexible InterConnect) and the lead time runs into months; for a single venue the product is overkill.
• ハイスタンダード (siptrunk.online) — a wholesale trunk with porting for 0120, 0800 and 0570; no technical parameters are published, so clarify everything when ordering.
• @niftyフォン-C — 050 numbers; the trunk did work in practice, but the service closes on 31.10.2026, so do not plan new connections on it.

Operators with no trunk for your own PBX#

• KDDI (KDDI-IPフォン, 光ダイレクト) — the operator accepts a direct SIP connection only for models on its approved equipment list, ours is not on it, and the SIP parameters are not published. The standard path for third-party equipment is a rented EGW gateway in the office: our PBX then sees an ordinary on-site SIP gateway rather than a KDDI trunk.
• SoftBank (おとく光電話) — the same logic: "if an IP PBX is connected directly to the line termination device, only devices that passed connection certification may be used", and the manager hands out the list. On 15.12.2025 the operator launched SmartCalling — an external line over a radio channel for cloud PBXs and CTI without a physical line and without a trunk gateway; whether a third-party cloud PBX may connect has to be asked separately.
• 03plus (グラントン) — a mass-market "landline number in your smartphone" service: an app, their own IP phone, a voice menu, forwarding, 0120/0800, 48 areas across 16 prefectures. There is no trunk for a third-party PBX — the number lives in their app or their handset. Two options remain: port the number to a provider with a trunk, or keep it as a separate line on a staff phone. This is also where the country's rule is easiest to see: an 03 number is not issued unless the company has an address or a place of business in Tokyo's 23 wards — and a "serviced shared office" for the sake of an address is sold as a paid add-on.

International providers with Japanese numbers#

Cards for the popular international providers are already in the catalogue when you add a provider — the server address and mode fill in automatically. The Japanese specifics:

• Twilio — Japanese landline, national and toll-free numbers; Elastic SIP Trunking works by IP or by a credential list, with no registration, which matches our "IP auth (no registration)" mode. Its document checks are the heaviest of all: an extract from the Japanese company register no older than 6 months, a letter on company letterhead, the representative's identity document (a residence card for foreigners), proof of address — with the address strictly inside the numbering area ("a PO Box is not acceptable"), all in Japanese script, plus a paper verification letter sent to that address. Resellers of numbers additionally need a copy of the recognised numbering use plan.
• DIDWW — Japan is within its coverage, and both modes are available: a static endpoint (by IP) and dynamic registration. Check the document requirements for Japanese numbers before ordering.
• AstraQom, Tata Communications, Telxi — specialise in Japanese numbers and termination; Tata and Telxi are listed among the certified SIP trunks for Japan by the 3CX PBX vendor.
• Telnyx, Vonage, Plivo, Bandwidth, Sinch, IDT Express, CommPeak — Japanese numbers do appear with them, but almost always "on request with documents"; confirm availability before paying.
• ⚠️ A common risk. A Japanese landline number bought "easily and without documents" almost certainly means the seller is breaching the numbering regime. If the ministry withdraws the recognition of their numbering use plan, the number goes dark with them.

Number porting#

• Since 14.01.2025 Japan has two-way porting of fixed numbers. Previously a number could only be taken away from NTT East and NTT West; now it moves between any fixed-line operators, including ひかり電話 numbers. The date and scope were announced by 18 operators on 12.11.2024.
• How it goes. The application is filed by the receiving operator, the work is chargeable (3,000 JPY per number at IPS PRO) and takes about two weeks. 03 and other landline numbers can be ported, as well as 0120, 0800 and 0570.
• ⚠️ 050 numbers cannot be ported — the 050 operators state this outright. If you change providers, the 050 number changes with them.
• A landline number is tied to an address. Moving within the same numbering area keeps the number; moving to another area does not.
• ⚠️ Ask in advance what the number becomes after porting. With some "cloud" providers a ported number stays a full 0AB-J with emergency calls, with others it loses individual properties. Put this in the contract.

Rules and paperwork#

If it does not work#

1. A ひかり電話 landline number does not register. That is expected: the NGN network is closed and registration is only possible from the line on the premises. You need an SBC gateway in the office or a different provider — see the section above.
2. Registration comes and goes, then the operator stops responding at all. With Rakuten it is the signalling rate: the registration must be refreshed exactly every 1800 seconds and outbound calls must not exceed one per second; offenders are filtered by IP. Agree the parameters in writing and contact us before you go live.
3. Calls connect but the voice menu does not hear the digits. With Rakuten and Basix tone dialling travels inside the audio, while our PBX needs RFC 2833 — ask the provider to switch the DTMF mode.
4. Three separate troubles on Basix. The provider sends the login instead of the number — the call is handled as "a call from this provider", but the line cannot be told apart by number. Its registration server and inbound server are different addresses while our "SIP host" field takes one, so there may be no inbound calls at all: ask the operator for the exact inbound address and contact us. And drops over UDP with a "513 Message Too Large" error are cured by switching the "Transport" field to TCP. With Cloco, ZivaPhone and Teleworks the number arrives in national format and the line is matched normally.
5. Outbound calls are rejected. Most likely the Caller ID ("Show as") field holds a number outside this operator's pool — in Japan that is directly prohibited. Leave the field empty.
6. Silence one way or both ways. Check the codecs: Teleworks has GSM in its default list, and some providers do not agree codecs at all. We need G.711 a-law or μ-law, or G.722.

Causes that are the same in any country are in If calls do not go through.

Frequently asked questions#

Can we use our 03 landline number in the PBX?#

Not directly, if it is a ひかり電話 number: it lives inside NTT's closed network, where a cloud PBX cannot register. There are two workable paths: port the number to a provider with an internet trunk (Cloco, ZivaPhone, Teleworks, IPS PRO), or keep it where it is and install a CC Architect SIP Connect gateway in the office for the PBX to reach over a trunk.

Which provider should we start with?#

If you need a number quickly and predictably — Rakuten OpenGate: the only large operator that permits a connection from a public cloud in writing (but the numbers are 050 only). If you need an actual landline number — Cloco, ZivaPhone or Teleworks: a trunk over the ordinary internet, published server addresses, and the called number delivered in a usable format. If nobody at the venue speaks Japanese — Brastel Basix.

Do we need a Japanese company?#

For a landline number — in practice yes: operators ask for an extract from the Japanese company register and an address inside the numbering area, and so do international providers (Twilio requires an address in the number's prefix area and posts a paper letter there). A 050 number is easier, but it is still issued under a contract with document checks.

Will emergency numbers 110 and 119 work?#

From a 0AB-J landline number — yes, emergency call support is mandatory for those. From a 050 number — normally not: operators warn outright that service numbers cannot be dialled from them. Keep an ordinary mobile phone in the dining room and brief the staff.

How long does connecting take?#

A 050 number from a provider that allows the cloud — 1 to 3 weeks with the documents. A landline number from a provider with an internet trunk — 2 to 4 weeks. ひかり電話 with an office gateway — from a month (line, gateway, connection profile). A corporate interconnect with NTT Com — months.

Can we run mass dialling over a Japanese trunk?#

Over Rakuten — no: the operator limits outbound calls to one per second per number and may stop the service without warning. With the others the call rate is set in the contract — ZivaPhone, for instance, raises it on request. Ask before connecting.

Sources#

All links checked on 10.09.2026.

Regulator and law

• 総務省 — the numbering regime and recognition of numbering use plans: https://www.soumu.go.jp/main_sosiki/joho_tsusin/top/tel_number/index.html
• 総務省 — quality requirements for 0AB-J IP telephony (PDF): https://www.soumu.go.jp/main_content/000357512.pdf
• 総務省 — anti-money-laundering rules for call answering and forwarding services: https://www.soumu.go.jp/main_sosiki/joho_tsusin/d_syohi/money/top.html
• TCA — guideline on preventing transmission of a different telephone number, 2nd edition of 24.10.2025 (PDF): https://www.tca.or.jp/information/pdf/20251024guideline.pdf

Providers

• Rakuten — IP電話 B2BUA OpenGate: https://comm.rakuten.co.jp/houjin/asterisk_ip/b2buaog/index.html
• Rakuten — FAQ on connecting a PBX: https://comm.rakuten.co.jp/houjin/asterisk_ip/faq/
• Rakuten — pricing: https://comm.rakuten.co.jp/houjin/asterisk_ip/price/
• Cloco — SIPトランク2: http://www.clocoinc.com/service/sip2
• Cloco — IP PBX connection manual, Ver 2.0.8 (PDF): https://www.clocoinc.com/image/manual/siptrunk_manual_Ver2.0.8.pdf
• Cloco — list of numbering areas: http://www.clocoinc.com/service/number
• ZivaPhone — SIPトランク: https://zivaphone.jp/business/siptrunk/
• ZivaPhone — allowed addresses and ports: https://zivaphone.jp/loginserverlist/
• Teleworks — SIPトランク: https://teleworksinc.com/product_lst/siptrunk/
• Brastel Basix: https://www.basix.jp/basixlp/
• Brastel — Basix PACKAGE Q&A: https://www.brastel.com/pages/jpn/intro/basixpck_faq.html
• CC Architect — SIP Connect: https://cc-arc.com/ccarchitect-sip-connect/
• NTT East — ひかり電話オフィスタイプ: https://business.ntt-east.co.jp/service/hikari_of/
• NTT Com — Arcstar IP Voice: https://www.ntt.com/business/services/voice-video/voip/ipvoice.html
• IPS — LIPSE SIPトランクサービス: https://ipsism.co.jp/domestic-telecom/ips-siptrunk-service/
• CloudNippon — SIP Trunks: https://www.cloudnippon.com/sip-trunks
• Oedo Telecom — SIP Trunk: https://oedotele.com/en/sip-trunk2/
• KDDI — approved equipment for KDDI-IPフォン: https://biz.kddi.com/service/ip-phone/pbx/
• SoftBank — SIP equipment for おとく光電話: https://www.softbank.jp/biz/voice/otoku-hikari/sip/
• 03plus: https://03plus.net/
• ハイスタンダード — SIPトランクサービス: https://www.siptrunk.online/

International providers

• Twilio — regulatory guidelines for Japan: https://www.twilio.com/en-us/guidelines/jp/regulatory
• Twilio — resellers of Japanese numbers must provide a valid numbering use plan: https://support.twilio.com/hc/en-us/articles/9956319880859-Notice-Resellers-of-Japanese-Phone-Numbers-must-provide-valid-Telecommunications-Numbering-Use-Plan-TNUP-November-2022
• 3CX — SIP trunk providers in Japan: https://www.3cx.com/partners/sip-trunks/japan/
• AstraQom — Japan SIP Trunks & DID: https://astraqom.com/en/japan

Related pages#

• Connecting a provider's number to the PBX — the general steps, trunk modes, network, connection check.
• Setting up SIP phones — how to connect desk phones and DECT to extensions.