How to keep your number when you switch network
By Monty · Updated 2 November 2026
Every UK network lets you bring your number with you when you join, and most of them call this "keep my number". You get a free PAC code from the network you're leaving and give it to the one you're joining, and your number moves across in a day or so. Where you hand the code over and how long the move takes is different at each network, so the sections below go through Vodafone, O2, Three, iD Mobile and Lebara one at a time.
Text PAC to 65075 from your current phone to get a free PAC code. Then give it to your new network, usually through its keep my number form or app once your new SIM is active. The number moves within about a working day and your old plan ends by itself, so don't cancel it first.
How does keeping your number work?
Moving a number between networks is called porting. The network you're leaving gives you a PAC, short for Porting Authorisation Code, and it lasts 30 days. You get it by texting PAC to 65075, and the PAC code guide has the other ways for every UK network. Make sure you ask for a PAC and not a STAC code, which gives you a new number and lets the old one go. You then give the code to your new network and it does the rest.
Your new SIM arrives with a temporary number. On switch day your real number replaces it, and there can be a short gap with no signal while that happens. Vodafone says it's around twenty minutes, and you might need to turn your phone off and on again afterwards.
Whatever you do, don't cancel your old plan before the number has moved. It ends by itself on switch day, and networks can't charge you notice for any time after that. Cancel first and the number goes with the plan, so you'd be relying on getting it back in time.
Where each network takes your PAC
| Network | Where you give the PAC | When the number moves |
|---|---|---|
| Vodafone | Keep my number form on its website | Within two working days, if the form arrives before 4pm |
| O2 | When you order, or Move my number in My O2 | Usually by 4pm on switch day, sometimes as late as 10pm |
| Three | PAC request form, once the new SIM is active | The next working day, if you send it before 5pm |
| iD Mobile | At checkout, or Switch to iD in the app | Within one working day |
| Lebara | Port-in form, once the new SIM is active | Usually within one working day |
By law the move should be done within one working day of your new network having your PAC. The times above are each network's own, counted from when you send the form.
How do I keep my number with Vodafone?
Vodafone uses an online form, and it's called Keep my number. You join Vodafone first and get your new SIM with its temporary number, then fill in the form with your PAC. Your old network might also want extra details like an account PIN, so check with them before you start.
Vodafone aims to move the number within two working days as long as the form arrives before 4pm on a weekday. A form sent at the weekend or on a bank holiday starts the next working day, and your confirmation email shows the date Vodafone got it.
The same form handles moves inside Vodafone. Going from pay as you go to pay monthly, the number moves the next working day if you ask by 4pm. Going the other way, from pay monthly to pay as you go, it only moves 30 days after you send the form, so leave yourself time.
How do I keep my number with O2?
O2 lets you give the PAC when you order or any time after. On the website it's under Switch to O2 and then Move my number, and in the My O2 app it's under Support and then Keep your number.
A request sent before 6pm switches sooner than one sent after. On switch day the number usually moves by 4pm, but O2 says it can take until 10pm, so don't panic if your old SIM is still working at teatime. If O2 misses the date it gave you, you're owed compensation.
If you're already with O2 you can keep your number when you move between pay as you go and pay monthly.
How do I keep my number with Three?
Three wants your new SIM working before you send the PAC. Put it in your phone, switch it on and wait for signal bars, and you might need to turn Wi-Fi off to see them. Then fill in Three's PAC request form.
Send it before 5pm on a weekday and your number should move the next working day. For a move on a Monday, the SIM has to be active by 5pm the Friday before. Three texts or emails you once the number has moved.
How do I keep my number with iD Mobile?
With iD Mobile you can give the PAC at checkout when you pick a plan or phone. If you've already ordered, it's on the Plan screen in the iD app or at my.idmobile.co.uk, under Switch to iD. Switching to iD with a PAC is free.
Plenty of people look for the PAC box while setting up the SIM and can't find it. It isn't there, because the PAC goes in through Switch to iD instead.
The one to watch is moving inside iD. iD's own staff say iD doesn't support moving a number from one iD account to another, so if you want a new iD deal and to keep your number, upgrade the account you already have rather than ordering a new plan as a new customer.
How do I keep my number with Lebara?
Lebara also wants the SIM active first. When you activate it you get a temporary Lebara number, and then you pick the date your old number moves across.
Lebara says the move usually takes no more than one business day. If the form says your PAC is invalid, ask your old network to confirm the code and that the number is still active before you try again.
Can I keep my number if I stay with the same network?
Yes. Upgrading or changing deal with the network you're already on keeps your number, and you don't need a PAC because a PAC only moves a number between networks. The trap is ordering the new deal as if you were a new customer, which gets you a new SIM with a new number. Ask for the upgrade on your existing account instead.
Moving between pay as you go and pay monthly is where networks differ. O2 keeps the number either way, Vodafone takes 30 days to move it from pay monthly to pay as you go, and iD can't move a number between two accounts at all.
What if the switch goes wrong?
Most moves go through without a hitch. When they don't, it's usually one of these.
- Your new network says the PAC is invalid. Check the code matches the number you're moving and is less than 30 days old. If it still fails, ask your old network for a new one.
- The number hasn't moved by the date you were given. Contact your new network first. Networks have to compensate you if the switch takes more than one working day.
- Your old network is blocking the move. Ofcom says to tell your new network, and an independent industry panel can overrule the old network and finish the move.
- You've already cancelled. You may still have time. O2 and giffgaff give PACs for up to 30 days after you leave, Sky for 31 days if you call, and Three for up to 90 days after your account closes. Ofcom also says a new network can take your number up to a month after you cancel.
Keeping your number when you move abroad
A PAC is also how you keep a UK number when you leave the country. Most people who move abroad hang on to theirs, because their bank, HMRC and WhatsApp all send codes to it. Paying for a UK plan just to receive those codes adds up, and a pay as you go SIM gets switched off if you forget to use it.
I've moved my own number twice. Before I left for Australia I took it from an O2 pay monthly plan to giffgaff pay as you go, and later I asked giffgaff for a PAC on its website from Australia and moved it into NumberNest.
NumberNest takes your number with a PAC in the same way a network would. Its texts arrive in the NumberNest app on your phone and on the web, and calls ring in the app over the internet, so there's no UK SIM to keep alive. It costs £5.49 a month. If you're moving for more than a few months, I'd bring the number over rather than keep paying for a plan you hardly use. NumberNest is on a waitlist while it gets ready to open, and the guide to keeping your UK number abroad compares every option.
Common questions
Does it cost anything to keep my number?
No. The PAC is free and so is the text to 65075. If you're still in a contract you may owe an early exit fee to your old network, and texting INFO to 85075 tells you how much.
Do I need to cancel my old contract?
No. Your old plan ends by itself when the number moves. Cancelling first can lose you the number.
How long does it take to keep my number?
Usually one working day once your new network has the PAC. Vodafone says it aims for two working days.
Will my contacts and texts move too?
Only the number moves. Your contacts and old texts stay wherever they're saved now, which is usually on your phone or in your iCloud or Google account.
Can I keep my number on pay as you go?
Yes. The PAC works the same way on pay as you go and pay monthly, whichever network you're joining.
Can I still keep my number if I've already cancelled?
Sometimes. Ask your old network for a PAC straight away. O2 and giffgaff give them for 30 days after you leave, Sky for 31 and Three for 90.