What is a STAC code and when you need one

A STAC — Service Termination Authorisation Code — is the code you use to **leave your mobile network and close your old account when you do *not* want to keep your number**. If you are switching to a new provider and are happy to take a brand-new number, a STAC is what lets you cancel cleanly with your old network in one quick step. It is the counterpart to a PAC code, which you use when you *do* want to take your number with you. Both are part of the UK's text-to-switch system, designed by Ofcom to make leaving a mobile network simple, free and fast. This guide explains exactly what a STAC is, when you need one rather than a PAC, how to get one for free by text, and what happens once you use it.

#What does a STAC code actually do?

A STAC authorises the termination of your contract with your current mobile network while discarding your existing phone number. When you give a STAC to your new provider (or use it to close your account), three things happen: your old network's contract is ended, your old number is given up (it is not transferred), and you move to your new provider on a new number. The 'authorisation' in the name is the key idea — the code proves to the networks that you, the account holder, genuinely want to leave, so the switch can happen quickly without lengthy verification or retention calls. It exists specifically for people who do not care about keeping their number: perhaps you are starting fresh, the number is one you never gave out, or you simply want a clean break. For anyone in that position, the STAC makes leaving as easy as sending one text.

#STAC or PAC — which do you need?

The choice between a STAC and a PAC comes down to a single question: do you want to keep your phone number? If yes, you need a PAC (Porting Authorisation Code), which transfers your number to your new network. If no — you are happy with a new number — you need a STAC. Most people switching networks want to keep their number, so PAC is the more common request; but a STAC is the right choice in plenty of situations, such as closing a second line, leaving a number you have only had briefly, escaping a number that has attracted spam, or simply wanting a fresh start. Importantly, you should only request the code that matches your intention, because the two have different outcomes — using a STAC permanently gives up your number, which cannot be undone once the termination completes.

If you are unsure, pause before requesting a STAC: giving up a number you have had for years, that is linked to your bank, contacts and online accounts, is a bigger deal than it first seems. In that case a PAC is almost always the better choice. Our UK phone number portability explained guide covers how keeping your number works in more detail, so you can decide with confidence.

#How to get a STAC code (free, by text)

Getting a STAC is deliberately simple and free, thanks to Ofcom's text-to-switch rules. From the phone on the account you want to close, text the word `STAC` to `75075`. Your network is required to respond — almost always within a minute, and by law within a short time — with a text containing your STAC code and important account information: any early-termination or exit charges you would owe for leaving before your contract ends, any outstanding balance, and any credit you are due. This information is there so you can make an informed decision before you actually switch. Requesting the code does not cancel your service or commit you to anything; it is purely an information step. You only actually leave when you hand the STAC to a new provider (or use it to terminate), so you can request it to check your exit charges and then decide at your leisure.

If you cannot text — for example the handset is broken, or it is a data-only line — you can also request a STAC by calling your network or, on some providers, through your online account or app. The text method is the quickest and is available to virtually everyone, but the alternatives exist so that no one is locked in by circumstance. Whichever route you use, the network must provide the same information about charges and credit. Keep the reply somewhere safe, because you will need the code itself to complete the switch — and note the expiry date, covered next.

#How long is a STAC code valid?

A STAC code is valid for 30 calendar days from the date it is issued. Within that window you can give it to your new provider to complete your switch, or use it to terminate your account. If you do not use it within 30 days, it simply expires and you can request a fresh one — there is no penalty and no limit on how many times you can ask. This generous window means there is no pressure: you can request the STAC to see your exit charges, take time to compare deals, and only act when you are ready. If your circumstances change and you decide to stay, you do nothing — an unused STAC lapses harmlessly and your existing service continues exactly as before. This is part of what makes text-to-switch so consumer-friendly: requesting the code carries no risk and commits you to nothing until you actively use it.

#What happens when you use a STAC

Once you give your STAC to a new provider (or use it to close the line), the termination process begins. Because you are not keeping your number, there is no port to coordinate, so the switch is typically very quick — your old contract ends and your new service starts on a new number, usually the next working day under the UK switching rules. Your old number is then released back into the pool and cannot be recovered, so make sure you have noted anything you need from the old line (contacts, two-factor settings, accounts tied to that number) before you switch. You will receive a final bill from your old network covering any outstanding charges, including the early-termination charge if you left before your minimum term — exactly the figures quoted in your STAC reply text, so there should be no surprises. After that, your relationship with the old network is closed.

It is worth pausing on the two-factor and account point, because it catches people out. Many online services — banks, email, social media, shopping accounts — use your phone number for security codes or recovery. If you give up that number with a STAC, those services will keep trying to text the old, now-cancelled number unless you update them first. So before you switch, change the phone number on your important accounts to your new number (or a temporary alternative), and check which services rely on the old one. This is the single most important bit of housekeeping when using a STAC rather than a PAC, precisely because the number is going away for good. Do it in advance and the switch is seamless; skip it and you may find yourself locked out of accounts that text a number you no longer control.

#STAC, PAC and PUK — don't mix them up

The UK mobile world has several similar-sounding codes, and confusing them causes real headaches, so here is the clear distinction. A STAC ends your contract and gives up your number (leave, new number). A PAC ends your contract but transfers your number to your new network (leave, keep number). A PUK (Personal Unblocking Key) is something else entirely — it unlocks a SIM that has been blocked after too many wrong PIN entries, and has nothing to do with switching networks; if your SIM is asking for a PUK, see our PUK code guide. On top of these, your SIM PIN, your network account password, and your voicemail PIN are all separate again. The trick, as with all phone codes, is to read precisely what is being asked and match it to your actual goal: switching with a new number means STAC; switching keeping your number means PAC; an unusable, blocked SIM means PUK.

Getting the right code first time saves time and avoids irreversible mistakes. The most consequential error is requesting and using a STAC when you meant to keep your number — because once the termination completes, the number is gone and a PAC can no longer rescue it. So before you text 75075, be certain you are happy to lose the number; if there is any doubt, request a PAC (text PAC to 65075) instead and keep it. Networks make both codes available freely and quickly, so there is no cost to choosing carefully. When in doubt, the safe default is to keep your number with a PAC, since you can always give a number up later but you cannot easily get a cancelled one back.

#Common STAC questions and situations

A few real-world situations help make the STAC concrete. Closing a spare or second line: if you have a tablet SIM, a second handset, or an old number you never use, a STAC is the clean way to terminate it without faffing over a number you do not want to keep. Escaping a spam-hit number: if your mobile number has been leaked and is buried in nuisance calls and texts, switching with a STAC gives you a fresh number and leaves the old, compromised one behind — a more decisive fix than blocking endless individual numbers. Starting fresh after a contract: some people simply prefer a clean new number when moving networks, and a STAC delivers exactly that. In each case the process is identical: text STAC to 75075, read the charges, then use the code with your new provider within 30 days.

People also ask whether requesting a STAC affects their credit or triggers retention calls. Requesting the code is an information step and does not by itself harm your credit; what matters is paying any final bill, including early-termination charges, on time. Some networks may text or call to try to keep you once they see a code requested, but you are under no obligation to engage — using the STAC with a new provider is enough to leave. And if you receive lots of unknown calls during or after a switch, remember you can always look a number up to see whether it is your old or new network, a genuine caller, or a nuisance, and use the general who called me checklist to identify anyone you are unsure about. Knowing your switching codes and your call-checking tools together makes changing networks genuinely painless.

#How text-to-switch came about and why it helps you

The STAC and PAC text-to-switch system did not always exist, and understanding why Ofcom introduced it explains why switching is so painless today. For years, leaving a mobile network meant phoning customer services, sitting through retention scripts, and sometimes being talked out of switching or delayed by deliberately awkward processes. Ofcom's reforms changed the rules so that you can leave by a single free text, your network must reply quickly with your code and a clear statement of any exit charges, and the switch completes rapidly — usually the next working day. The aim was to remove the friction that kept people on poor-value deals simply because changing was a hassle. The STAC is the 'leaving without keeping my number' half of that system, and the PAC is the 'keeping my number' half. Both put you in control: you request information for free, with no obligation, and you decide when (or whether) to act. That balance of power is a big part of why UK mobile switching is now considered among the more consumer-friendly in the world.

There are a few practical protections baked in that are worth knowing. Your network cannot refuse to give you a STAC or PAC, and cannot make you call a retention line to get it — the text route must work. The code reply must spell out any early-termination charge, so you are never ambushed by a surprise bill. And because requesting a code does not start the clock on cancellation, you can shop around freely: get your STAC, compare new-provider deals at your leisure, and only commit when you find one you like, all within the 30-day validity window. If a network ever drags its feet or makes the process difficult, that itself is a breach of the rules you can complain about. For the bigger picture of how switching and number transfers are regulated, our UK phone number portability explained guide is a useful companion, and our guide to UK mobile networks by 07 prefix helps you understand which networks the various mobile ranges belong to as you compare providers.

#A worked example: switching with a STAC

To make the whole process concrete, here is how a typical STAC switch plays out from start to finish. Say you have a spare mobile line you barely use, on a number you never gave out, and you want to move it to a cheaper SIM-only deal with a new provider and are happy to take a new number. Step one: from that phone, you text STAC to 75075. Step two: within about a minute, your network texts back your STAC code along with a note that, since you are out of contract, there are no early-termination charges and you have a small credit balance owing to you. Step three: you take out the new SIM deal and, when prompted during sign-up, give the new provider your STAC. Step four: the new provider arranges the switch; your old line is terminated and your new SIM activates, typically by the next working day, on a brand-new number. Step five: a final bill arrives from the old network settling the account, matching the figures in your STAC text. The whole thing takes a few minutes of your time and a day to complete.

Now contrast that with the housekeeping you would do if this were your main number that you used everywhere. Before texting STAC, you would first ask yourself whether you really want to lose the number — and in most cases for a main line, the answer is no, so you would request a PAC instead and keep it. If you genuinely did want a fresh main number (say, to escape relentless spam), you would, before switching, update your number on your bank, email, social media, shopping accounts and any two-factor or recovery settings, and tell key contacts your new number is coming. Skipping that step is the most common STAC regret: people give up a number, then find verification codes and account recovery messages still being sent to a dead line. So the worked example has two lessons — the mechanics are trivially easy, and the only real care needed is deciding whether you truly want to part with the number and, if so, doing your account housekeeping first. If unwanted calls are the reason you are switching, it is also worth first trying to look up and block the worst offenders, since that sometimes solves the problem without changing your number at all. Equally, if the nuisance is mainly voicemail filling up with junk, you might simply turn voicemail off rather than abandon the number — our how to turn off voicemail guide shows how, and it is a far smaller step than giving up a number you have had for years.

It is also worth thinking about timing. Because a STAC switch completes quickly — usually the next working day — there is little dead time between leaving and being set up on your new provider, but you should still avoid switching at a moment when you are relying heavily on the old number for something time-critical, such as an imminent delivery, a job application callback, or a bank security process mid-flight. Give yourself a day or two of overlap to update accounts and tell key contacts, request the STAC when you are ready, and complete the switch when nothing urgent is pending. That little bit of planning turns an already-easy process into a completely seamless one, with no missed calls or locked-out accounts in the gap.

#Bottom line

A STAC (Service Termination Authorisation Code) lets you leave your mobile network and close your account without keeping your number — you get a new number with your new provider. Get one free by texting `STAC` to 75075; your network replies with the code plus any exit charges, the code lasts 30 days, and requesting it commits you to nothing until you use it. Choose a PAC (text PAC to 65075) instead if you want to keep your number, and don't confuse either with a PUK, which just unblocks a SIM. Before using a STAC, update your two-factor and account details to your new number, since the old one is cancelled for good. For more, see our PUK code guide and UK number portability explained.