MNP in Japan for Foreign Residents: Keep Your Phone Number When Switching Carriers

Mobile Number Portability, usually called MNP, allows an eligible Japanese mobile number to move to another carrier. The number can stay the same, but the contract around it does not. The plan, SIM or eSIM, account login, billing method, optional services, carrier email, support channel and activation procedure can all change.

Foreign residents should prepare MNP as both a telecom procedure and an identity-matching procedure. The name, date of birth and other subscriber information held by the current carrier may need to agree with the new application. A small mismatch can delay the move even when the number itself is eligible.

Safe order: compare the new provider, confirm phone compatibility, prepare matching identity and payment details, start MNP through the supported route, receive the new SIM or eSIM, complete the line switchover and then test calls, SMS and mobile data.

MNP is easiest when treated as a planned migration rather than a cancellation. Before applying, record the old carrier account holder, exact mobile number, current plan, device-payment balance, carrier email, family or home-internet discounts and services billed through the carrier. Then record the new provider, application route, SIM type, activation method and support channel. This simple record shows what moves automatically, what needs reconfiguration and what remains billed separately.

Also note the date by which the old service must remain usable, the expected SIM arrival date and the hours during which line activation is accepted. Planning those three times prevents a reservation from expiring or a transfer from being attempted after support has closed.

Quick Answer: What MNP Keeps and What It Does Not Keep

Item Usually kept? What to check
Eligible Japanese mobile number Yes The number remains active and MNP completes correctly
Current monthly plan No The new provider starts a separate plan
Physical SIM or eSIM profile No A new SIM or profile is normally issued
Phone handset Often SIM lock, bands, VoLTE and compatibility
Device installment balance No transfer Payments may continue with the old provider
Carrier email Not automatically A separate portability service may be required
Points and bundle discounts Not automatically Review household and linked-service effects
Voicemail and options No Configure them again where needed

One-Stop or Reservation Number?

Japan has two practical MNP routes. The one-stop method lets eligible customers complete an online transfer through the new provider without first obtaining an MNP reservation number. It works only when the providers and application route support it. The traditional route uses an MNP reservation number issued by the current provider and entered during the new-provider application.

Route Best used when Main limitation
MNP One-Stop Both providers support it and the application uses the supported online route It may not be available in shops or for every account condition
Reservation-number route One-stop is unsupported or the selected route requires a number The reservation has a validity period
Brand-to-brand transfer Moving between related brands with a special procedure Instructions may differ from ordinary MNP
Support-assisted route The account has a name mismatch, representative or exceptional condition Extra documents and time may be required

NTT Docomo states that a reservation number is not required when applying online with the one-stop method. Rakuten Mobile also explains that one-stop can avoid the reservation-number step for supported carriers, while customers coming from unsupported providers use the traditional route.

Do not assume one-stop is universal. Check the new provider’s current application page immediately before starting. A provider may support one-stop online while requiring a reservation number through another channel.

Do Not Cancel the Old Line First

Ordinary cancellation and MNP are different actions. When the goal is to keep the number, begin with the new provider’s MNP instructions or the old provider’s reservation-number process. Cancelling the current line before the transfer can make the number unavailable for MNP.

The old line generally remains usable until the new provider completes the switchover. Exact timing depends on the provider, SIM delivery, eSIM setup and the customer’s activation action. A short interruption can occur while the number moves between networks.

Action Effect on the number Safer choice
Ordinary cancellation The number may be disconnected Use the MNP route
Request reservation details The old line normally remains active Continue service until transfer completes
Start one-stop The new provider coordinates the transfer Finish every authentication screen
Complete activation The number moves and the old line closes Test the new line immediately

Match Subscriber Information Before Applying

MNP can stop when information held by the old provider does not match the new application. This is common with middle names, Roman-letter spacing, name order, old addresses, changed legal names and contracts originally created by a family member or employer.

Prepare the exact document combination required by the new provider. Our Japanese voice-SIM document checklist covers identity, address and payment preparation.

Record Confirm before MNP Possible problem
Current carrier account Subscriber name, date of birth and active number The contract belongs to another person
Identity document Legal spelling, address and validity The new provider cannot verify the applicant
New-provider form Name order, middle name, address and email Typing differs from official records
Payment method Accepted issuer and permitted holder The card or bank account is rejected
Reservation details Correct number and enough validity The reservation expires during screening

Before MNP: Compare the New Provider Properly

Keeping the number does not make the new contract suitable. Compare the normal monthly charge, data allowance, voice-call conditions, support, coverage, compatible devices, payment methods, cancellation procedure and options. Our major carriers vs low-cost providers guide separates major carriers, online plans, sub-brands, MVNOs and international-focused services.

  • Check coverage at home, work, school and regular train routes.
  • Confirm the exact phone supports the network and voice service.
  • Review the ordinary price after campaigns end.
  • Check whether in-person help is available.
  • Confirm the accepted payment method before beginning MNP.
  • Check eSIM reissue and physical-SIM replacement procedures.
  • Review roaming and overseas SMS requirements.
  • Check whether carrier email or bundle discounts will be lost.

One-Stop Method: Practical Flow

Step What to do What to save
1. Start with the new provider Select MNP and one-stop when offered Application number and selected plan
2. Authenticate with the old provider Follow the redirect and approve the transfer Confirmation screen or email
3. Return to the application Complete identity, address, payment and SIM details Submitted information
4. Wait for screening or delivery Keep the old line active and monitor email Shipment or eSIM notice
5. Activate the new line Use the provider’s switchover procedure Activation completion time
6. Test service Check calls, SMS and mobile data Errors and screenshots

Do not close the browser during authentication unless the provider says the procedure is complete. Pop-up blocking, expired login sessions and unfinished consent screens can leave the request incomplete. Save the application number before leaving the page and use the same browser session when instructed.

Two-Stop Method: Reservation Number Flow

When one-stop is unavailable, obtain an MNP reservation number from the current provider and use it during the new-provider application. The exact validity and required remaining period are stated by the providers. Do not wait until the final day to submit an application that still needs screening and SIM delivery.

Stage Check Common mistake
Request reservation details Use the current provider’s official route Submitting ordinary cancellation
Record the information Number, expiry date and subscriber name Typing one digit incorrectly
Apply to the new provider Choose MNP and enter details exactly Selecting a new-number application
Complete screening Respond to document requests promptly Allowing the reservation to expire
Receive SIM or eSIM Follow the new provider’s setup order Removing the old SIM too early
Switch the line Activate during the permitted period Waiting until an urgent call is expected

Plan the Switchover Time

Choose a time when a temporary interruption will not create a serious problem. Avoid switching immediately before a flight, hospital appointment, job interview, bank transfer, important delivery or account-recovery procedure. Keep another reachable contact method available until the new line is tested.

Keep another internet connection available. Wi-Fi or backup data can be essential while downloading an eSIM, reading activation instructions, signing into the provider account or contacting support.

  • Charge the phone and update the operating system.
  • Save the new-provider login and application number.
  • Keep the old SIM installed until instructed otherwise.
  • Do not delete an active eSIM profile during setup.
  • Write down APN settings where required.
  • Tell important contacts that a short interruption is possible.
  • Keep SIM packaging until every function works.

Physical SIM and eSIM Have Different Risks

Point Physical SIM eSIM
Delivery Wait for shipping or collection Wait for screening and profile instructions
Installation Insert the correct SIM after the transfer step Install the profile on the intended device
Backup connection The old SIM can remain until switchover Wi-Fi may be required
Device change The card may move to another compatible phone Transfer or reissue may be required
Common error Wrong slot, SIM lock or APN Wrong EID, deleted profile or incomplete activation

For eSIM, confirm that the exact device supports the provider, that the EID belongs to the intended phone and that Wi-Fi is available during installation. For physical SIM, confirm the correct size, slot and SIM-lock status. In either case, do not assume data connectivity proves that normal voice calls and SMS are working.

Protect Two-Factor Authentication During the Switch

MNP keeps the number, but account access can still be disrupted while the old line stops and the new line activates. Prepare banking, email, messaging and password-recovery access before beginning. The goal is to avoid depending on one SMS code during the exact period when the line is moving.

  • Confirm access to the email used by both providers.
  • Save backup codes for important accounts.
  • Back up authenticator apps or confirm transfer procedures.
  • Do not reset the phone during MNP.
  • Keep another trusted device signed in where appropriate.
  • Test incoming SMS after activation before changing settings.
  • Keep recovery contact information current.

Old-Carrier Services Need Separate Attention

Old service Possible result after MNP Action
Device installments Payments may continue Keep the billing method active
Carrier email The address may stop Check portability deadlines and fees
Family or home bundle Other charges may change Calculate the household effect
Points and rewards Rules vary by program Keep account access and read terms
Insurance and options Some end; others continue Review every service on the final bill
Carrier billing Content payment may stop Change the payment method beforehand

Do not close the old-provider account immediately after the line moves. Keep login access until the final invoice, device balance and optional services are confirmed. Save copies of the old contract summary and final bill because support may need the account number after the phone line has already transferred.

Mobal and Product-Specific MNP Rules

International-focused providers can have product-specific limits. Mobal port-in and port-out availability differs by product generation and plan type. Do not assume every physical SIM, eSIM or Voice Lite product supports the same route. Read our Mobal SIM and eSIM guide and confirm the exact product shown in the account.

When the provider uses a special support form instead of ordinary one-stop or reservation-number flow, follow that product’s instructions before cancelling anything. Save the product name, purchase date, current plan and support ticket number so the provider can identify the correct transfer rules.

After Activation: Test in the Correct Order

Test How to check If it fails
Network registration Confirm signal and the intended carrier Restart and check network selection
Outgoing call Call a safe known number Check voice-line selection and VoLTE
Incoming call Call the number from another phone Confirm switchover completion
SMS Send and receive a normal message Check selected SMS line and provisioning
Mobile data Turn off Wi-Fi and open a webpage Check APN and data-line settings
Authentication Test a non-critical SMS login Wait for provisioning and contact support
Voicemail and options Open the new-provider account Configure services again

Test incoming calls before assuming the number is fully transferred. Then test outgoing calls, SMS in both directions and mobile data away from Wi-Fi. When dual SIM is enabled, confirm which line is selected for calls, SMS and data. Take screenshots of error messages before changing several settings at once.

Troubleshooting Table

Problem Likely cause Next check
One-stop does not appear Unsupported provider, channel or account Use the reservation-number route
Old-provider authentication fails Wrong login or restricted account Recover access through the old provider
Reservation number rejected Typing error, expiry or low remaining validity Check the original notice
Subscriber mismatch Name, birth date or holder differs Correct the old account or contact support
Old line stopped; new line fails Activation or SIM setup is incomplete Use Wi-Fi and follow the activation guide
Calls work; data fails APN or data-line setting Use official device instructions
Carrier email stopped It was not included in MNP Check whether portability is still available
Unexpected final bill Device balance, delayed usage or options Compare the invoice with the old contract

Support Message Template

Hello. I am switching my Japanese mobile number from [old provider] to [new provider] using [MNP One-Stop / an MNP reservation number].

The number is [number], the current subscriber name is [exact name], and my new application number is [number]. The old line currently shows [active / no service], while the new account shows [status].

I have received [physical SIM / eSIM instructions] and completed [steps]. Please confirm whether the MNP authorization and line switchover are complete and tell me the next step without cancelling the number.

Include the exact phone model, SIM type, time of the attempted switchover and any displayed error code. Do not include passwords, full payment details or one-time authentication codes in an ordinary support message.

Official MNP Sources

MNP routes, supported providers, reservation-number rules, activation hours, fees, campaigns and required documents can change. Confirm both providers’ current official pages before beginning.

Final MNP Checklist

  • Confirm the number is active and eligible.
  • Compare the new provider before moving the number.
  • Check device, SIM and eSIM compatibility.
  • Match the subscriber name and identity information.
  • Choose one-stop or the reservation-number route.
  • Do not submit ordinary cancellation.
  • Keep the old line active during screening and delivery.
  • Plan the switchover away from urgent calls.
  • Keep Wi-Fi or another connection available.
  • Protect authentication and recovery access.
  • Review carrier email, bundles, options and device payments.
  • Complete the official activation procedure.
  • Test calls, SMS and mobile data.
  • Save the final old-provider bill and new contract.

Best next action: open the new provider’s current MNP page first. Confirm whether the old provider is supported by one-stop. When it is not, obtain reservation information through the old provider’s official procedure without cancelling the line.

MNP Does Not Transfer the Device Installment

The phone number can move while remaining handset payments continue under the old provider agreement. Read the phone installment, SIM-only and payment-method guide for foreign residents.

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