Mobile Number Portability (MNP) lets you keep your phone number when you move to a different carrier. You do not need to hand out a new number to contacts, update business cards, or re-register with every service you use.
The process involves three things: collecting a transfer credential from your current carrier, providing it to your new carrier, and waiting for the port to complete — a matter of hours in most countries.
This guide explains how the system works technically, the exact steps for the US, UK, and Australia, what can go wrong, and how to protect services that rely on SMS during the switch.
What Is Mobile Number Portability?
MNP is a regulatory and technical framework that allows a mobile subscriber to retain their phone number when transferring service to a different carrier. Without it, your number would belong to the carrier, not to you, and switching would mean losing it permanently.
Phone numbers are assigned within the ITU-T E.164 numbering plan, which gives each country a country code and allocates number ranges to carriers. Historically, this meant a number was permanently tied to the carrier that owned the range. MNP breaks that tie by introducing a routing layer that redirects calls and messages to wherever the number currently lives.
The first country to implement MNP was Singapore in 1997. The ITU subsequently published Recommendation Q.769.1 (1999), which defined the signalling protocol for number portability within SS7 networks. Today, most countries with significant mobile markets have mandated MNP by law.
The regulatory goal is competition: if switching carriers means losing your number, many customers will stay with a carrier they dislike rather than go through the disruption. MNP removes that barrier.
How MNP Works Technically
Understanding the technical mechanics helps explain why porting takes time and why certain failure modes exist.
The Porting Database
When a number is ported, it is registered in a central or distributed porting database — sometimes called a Number Portability Database (NPDB) or a Ported Number Register. Different countries use different architectures: some use a single national database, others use decentralised query systems between carriers.
Every time a call or message is routed toward a ported number, the originating network queries this database to find which carrier currently hosts the number, then routes traffic accordingly. This lookup happens in real time using SS7 signalling.
ENUM and IP Routing
For VoIP and IP-based messaging networks, ENUM (E.164 Number Mapping, defined in IETF RFC 6116) provides an equivalent DNS-based lookup mechanism. ENUM maps a telephone number to a URI, allowing VoIP systems to locate the correct endpoint without relying solely on SS7. This is how services like WhatsApp and iMessage can find the right destination for a number that has been ported.
MSRN and Call Routing
In GSM and UMTS networks, a Mobile Station Roaming Number (MSRN) is used for call delivery. When a call arrives at the carrier that previously owned the number range, that carrier (or the routing layer) uses the ported number database to obtain an MSRN, which points to the number’s current home network. The call is then forwarded transparently — the caller hears nothing unusual.
The Port-In / Port-Out Model
Every port has two sides:
- Port-out: your current (losing) carrier releases the number.
- Port-in: your new (gaining) carrier claims it and updates the routing database.
In most countries, the gaining carrier initiates the process after you provide authorisation. The losing carrier validates your identity details, confirms no contractual block exists, and releases the number on the agreed date.
The MNP Process: Step-by-Step
The exact steps differ by country, but the underlying sequence is the same.
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Gather your account details — You need your account number with the current carrier and a transfer credential (PIN, transfer code, or authorisation code depending on the country). In most markets, these are not the same as your online login password.
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Request a transfer code from your current carrier — In the US this is called a Number Transfer PIN. In the UK it is a PAC code obtained by texting 65075. In Australia the gaining carrier handles identity verification directly, so you do not need a separate code.
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Sign up with your new carrier — During the sign-up flow, provide your number and the transfer credential. The new carrier submits the port request to the database on your behalf.
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Activate your new SIM or eSIM — Your new carrier will issue a physical SIM card or an eSIM profile. Do not activate it until the port request has been submitted; activating early can sometimes interfere with the transfer.
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Wait for the port to complete — You will lose service on your old SIM for a period ranging from a few minutes to a few hours. When the new SIM shows signal and your number works for calls and texts, the port is done.
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Confirm and keep your old SIM until verified — Before discarding or returning the old SIM, send a test message to yourself and receive a call. Only then is it safe to dispose of the old SIM.
How Long Does Porting Take?
Port timing is set by national regulation and varies significantly.
| Country | Typical completion time | Regulatory basis |
|---|---|---|
| United Kingdom | Within 1 working day of PAC submission | Ofcom switching rules (2019) |
| Australia | ~3 hours for simple ports | ACMA industry standard |
| United States | 1 business day (simple port) | FCC Local Number Portability rules |
| European Union | Within 1 working day | Directive 2002/22/EC / EECC 2018/1972 |
| Germany | 1 working day (gaining carrier initiates) | Bundesnetzagentur, §59 TKG |
| France | 1 working day for prepaid; up to 3 days for postpaid | ARCEP Decision No. 2022-2148 |
| Canada | 2.5 hours for wireless simple ports | CRTC Wireless Code (2013, revised 2017) |
| Japan | Same day to next business day (online) | Ministry of Internal Affairs guidelines |
“Simple port” typically means a standard postpaid or prepaid consumer line. Business accounts with multiple lines, or ports involving a change of account holder name, may take longer.
Country-Specific Rules
United States
The FCC’s Local Number Portability (LNP) mandate requires US carriers to port numbers upon a valid customer request. To port your number, you need:
- Your account number — visible on your bill or in your carrier’s account portal.
- A Number Transfer PIN — a separate code (distinct from your account password or billing PIN) that most carriers now require you to set up in advance. If you have not set one, do this before contacting the new carrier.
In practice, US carriers generally do not charge porting fees, and the FCC prohibits carriers from refusing a port due to an outstanding balance. (FCC: Porting — Keeping Your Phone Number When You Change Providers)
The FCC mandates that simple ports be processed within one business day, though the actual SIM activation window may extend several hours into that period.
United Kingdom
Ofcom introduced the Text-to-Switch system in July 2019. To get your PAC code:
- Text PAC to 65075 from the number you want to port.
- Your current carrier must send the PAC within 60 seconds, free of charge.
- The PAC is valid for 30 days.
- Give the PAC to your new carrier when signing up. The port must complete within one working day of the new carrier receiving a valid PAC.
If you want to leave your carrier without keeping your number, text STAC to 75075 instead. You will receive a Service Termination Authorisation Code.
Australia
In Australia, the gaining carrier — not the customer — handles the port-out process. You authorise the new carrier to request the transfer on your behalf. ACMA rules require the gaining carrier to verify your identity before proceeding, as a measure against fraudulent porting.
Industry service levels require 90% of simple mobile ports to complete within 3 hours and 99% within 2 business days. There is no fee for porting. (ACMA: Keep or transfer your phone number)
The pre-porting identity verification requirement was strengthened by the Telecommunications (Mobile Number Pre-Porting Additional Identity Verification) Industry Standard 2020, introduced specifically to combat port-out fraud.
European Union
EU Directive 2002/22/EC (the Universal Service Directive) requires that subscribers be able to retain their phone numbers when switching providers, and that the process must complete within one working day. Porting must be free of charge. Note: this directive has been superseded by the European Electronic Communications Code (Directive 2018/1972), which maintains and reinforces these number portability obligations for member states.
Individual member states vary in how they implement the request process — some use a PAC-style code system, others have the gaining carrier handle the transfer directly.
Germany
Germany implements the EU number portability rules through §59 of the Telekommunikationsgesetz (TKG). The gaining carrier initiates the port request on the customer’s behalf. The Bundesnetzagentur (Federal Network Agency) mandates completion within one working day for standard consumer ports. The process is free of charge for the subscriber. If you hold a German number under a contract with a minimum term, you remain liable for any early termination fee, but the fee cannot be used to block the port itself.
France
French number portability is regulated by ARCEP (Autorité de Régulation des Communications Électroniques et des Postes). Decision No. 2022-2148 requires that simple mobile ports complete within one working day for prepaid lines. Postpaid ports may take up to three working days in practice. Porting is free of charge. The gaining carrier handles the port request after you provide your RIO (Relevé d’Identité Opérateur) code — obtain it by calling 3179 from your current mobile line (free of charge, available 24/7). The RIO is valid for 30 days.
Canada
The CRTC (Canadian Radio-television and Telecommunications Commission) Wireless Code mandates that simple wireless port requests complete within 2.5 hours. Porting is free. You provide your account number and transfer PIN to the new carrier, which initiates the port. The CRTC Code also prohibits carriers from imposing a cancellation fee solely for porting away; however, remaining device financing obligations or contract early termination fees still apply.
Japan (brief note)
Japan operates two parallel systems. The traditional method requires obtaining a reservation number (MNP予約番号) from the current carrier, valid for 15 days. Since May 24, 2023, a One-Stop MNP system allows the entire transfer to be completed on the new carrier’s website, without contacting the old carrier. The One-Stop system is online-only. (MIC Japan)
What You Need to Provide
Regardless of country, you will be asked for some combination of the following:
- Phone number to be ported (the number you want to keep).
- Account number with the current carrier — this is not your phone number; it is an internal identifier on your billing account.
- Transfer credential — a PIN, transfer code, or authorisation code (PAC in the UK; Number Transfer PIN in the US). In Australia, the gaining carrier verifies your identity directly.
- Registered name — the name exactly as it appears on the account. Even small discrepancies (a middle name, a hyphen) can cause the port to be rejected.
- Registered address — the billing or service address on the account.
For eSIM ports, the process is the same. After the port completes, your eSIM profile on the new carrier’s network will respond to your ported number.
If your current carrier’s device is SIM-locked, resolve that before initiating a port. A locked device will not connect to the new carrier even after the number transfers successfully.
Some carriers require you to have been a customer for a minimum period (typically 30–90 days) before they will unlock a device. Plan ahead if you are approaching the end of a contract and want to port out immediately upon expiry.
Common Failure Modes
The majority of failed or delayed ports fall into a small number of categories.
Name or address mismatch — The most frequent cause. The name submitted to the losing carrier must match the account exactly. If your account shows “Robert Smith” and you submit “Bob Smith,” the port will be rejected. Check your carrier’s online portal for the exact registered name before initiating a switch.
Wrong transfer credential — Using your account login password, billing PIN, or SIM card PIN instead of the specific Number Transfer PIN (US) or PAC code (UK). These are different things. Request the correct credential from your current carrier before starting the process.
Account under contract lock or administrative hold — Some carriers place a 60-day lock on accounts after a recent SIM swap or account change. If your account has been recently modified, contact your carrier to confirm whether a porting hold applies.
Outstanding balance — While carriers in the US and most other markets cannot legally refuse to port because of a balance, some carriers may attempt to delay the process or notify the customer. If this happens, contact your national regulator.
Prepaid account with insufficient balance — Some prepaid accounts must have a non-zero balance to remain active long enough to complete a port. Top up before initiating if in doubt.
eSIM activation race condition — When porting to a carrier that issues an eSIM, some platforms prompt you to download and activate the eSIM profile immediately after submission — before the port-out from the old carrier has completed. If you activate the eSIM too early, the profile may bind to the new carrier’s network before the number transfer registers, resulting in the eSIM showing signal but the ported number not yet routed correctly. The fix is to wait for an explicit confirmation from the new carrier that the port is complete before tapping “Activate” on the eSIM install prompt. Typically this takes 15–60 minutes after submission; do not rush the activation step.
Account locked by the customer — Since the FCC’s 2023 SIM-Swap and Port-Out Fraud rules (FCC 23-95) came into effect, US carriers offer free account locking features that block port-out requests as a fraud prevention measure. Verizon offers separate SIM Protection and Number Lock features; AT&T introduced Wireless Account Lock in 2025. If you have enabled such a lock, disable it before requesting a port.
Risks During the Port
SMS 2FA Interruption
The most practically important risk. During the window when the number is transitioning — which can range from minutes to a couple of hours — SMS messages may not be reliably delivered to either SIM. If you trigger an SMS-based two-factor authentication request (for a bank, email account, trading platform, etc.) during this window, you may not receive the code and could be locked out temporarily.
Mitigation: Before you start the port, identify any critical services that send 2FA codes to your number. Log in to those services before initiating the port, or wait until you have confirmed the port is complete before using them.
A further mitigation strategy is to temporarily switch critical accounts from SMS-based 2FA to an authenticator app (such as Google Authenticator, Authy, or Apple Passwords) before the port. Authenticator apps generate codes locally and do not depend on SMS delivery, so they continue to work without interruption throughout the port window. After the port completes, you can keep the authenticator app active — doing so also improves your long-term security posture, since SMS 2FA is vulnerable to SIM-swap attacks.
Voicemail Loss
Voicemail messages stored on your old carrier’s servers are not transferred during a port. They remain accessible only on the losing carrier’s system, usually for a limited period after the account closes. Download or note any important voicemails before the port completes.
To preserve access to voicemails that arrive during the transition window, set up call forwarding on your old number to a secondary number or a VoIP number before initiating the port. This way, any calls that land on the old routing path can still reach you while the porting database updates propagate across networks — a process that can take several hours for international carriers.
Alternatively, consider switching to a third-party visual voicemail application (such as Google Voice in the US, or YouMail) before the port. These services store voicemails in the cloud independently of your carrier, so they survive a carrier switch without any data loss. Once the port completes, re-link the app to your ported number on the new carrier.
Family Plan and Shared Account Complications
If your line is part of a shared family plan, porting one line may affect billing for the whole account. The remaining lines may move to a different pricing tier. Confirm with your carrier how a partial port-out affects the remaining plan members.
Most family plans use line-count tiers for pricing — for example, a four-line plan at a lower per-line rate than a three-line plan. Removing one line via a port-out may automatically bump the remaining lines to the higher-priced tier, increasing the monthly bill for everyone still on the account. Before porting, ask your current carrier for the exact new rate that would apply to the remaining lines.
Additionally, lines on a family plan are typically owned by the primary account holder, not by the individual line user. If you are not the primary account holder, you may need the account holder to authorise the port-out on your behalf — either by providing the account PIN or by contacting the carrier directly. Without this authorisation, the losing carrier will reject the port request. In some cases, where the primary account holder is no longer reachable (e.g., a deceased family member or a former employer), you may need to initiate a formal account ownership transfer before the port can proceed.
Business Accounts
Business accounts with multiple lines often have different porting procedures. They may require a letter of authorisation (LOA) or involve longer processing times. Individual lines on a business account generally cannot be ported individually without the account holder’s authorisation.
For bulk ports — where a company is moving all lines from one carrier to another — carriers typically provide a dedicated migration team and a structured port window (often scheduled overnight or over a weekend to minimise operational disruption). Bulk ports require a signed LOA listing all numbers to be transferred, and the account’s tax identification number or business registration number is usually required for identity verification. Allow at least two weeks of lead time when coordinating a bulk business port.
International Number Porting
MNP is a national framework — numbers cannot be ported between countries. If you are an international resident who wants to keep a foreign number while using a local carrier, you will need a separate solution (such as a VoIP number or a dual-SIM setup). For more on how MVNOs compare on international features, see the MNO vs MVNO comparison guide.
Some travellers and expatriates use a dual-SIM or dual-eSIM device to maintain both a home country number and a local data SIM simultaneously. On modern iPhones and Android devices that support two active eSIM profiles, this allows receiving SMS on a home number (important for 2FA) while routing data calls through a cheaper local plan. This is not number porting — both numbers remain on their original carriers — but it is an effective workaround when cross-border porting is not possible.
FAQ
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Will I lose my number if I cancel first?
Yes. Never cancel your old account before the port completes. Cancellation releases the number back to the carrier’s pool. Once released, it can be reassigned to another subscriber, and recovery is either impossible or requires a lengthy dispute process with the carrier. Always wait for explicit confirmation from your new carrier that the port is complete before contacting your old carrier about cancellation.
What if my port is rejected?
The new carrier is required to inform you of the rejection reason. The most common reasons are a name or address mismatch, an incorrect transfer PIN, or an active account lock. Fix the specific mismatch, re-request the port with corrected details, and the process restarts. If the losing carrier refuses to port without a valid regulatory reason, you can file a complaint with your national regulator (FCC in the US, Ofcom in the UK, ACMA in Australia, or Bundesnetzagentur in Germany).
Can I port an eSIM to a physical SIM, or vice versa?
Yes. The port process is credential-based, not tied to the physical form of the SIM. When porting from a physical SIM carrier to a carrier that issues eSIMs, the new carrier will provide a QR code or activation code after the port completes. When moving from eSIM back to a physical SIM, the new carrier ships or provides a physical card, and the port transfers the number onto it. The transition window and risks are the same regardless of SIM type.
Related Guides
- What Is a SIM Card? — Understanding the physical credential that MNP transfers between carriers.
- What Is an eSIM? — How porting works when your new carrier issues an eSIM instead of a physical card.
- SIM Lock Explained — Check whether your device is locked to your current carrier before you port.
- What Is an MVNO? — Many people port to an MVNO to reduce costs; understand what you are moving to.
- MNO vs MVNO vs Sub-Brand Comparison — Side-by-side analysis of network quality, peak-time speeds, pricing, customer service, and 5G access by carrier type, with a decision tree by user profile.