A pay as you go SIM connects your phone to a UK network without a contract. You buy credit or a bundle when you want it, stop whenever you like, and nobody runs a credit check. Below we explain how to pick a network, choose between a SIM card and an eSIM, get set up and bring your old number with you.
What is a pay as you go SIM card?
A pay as you go SIM is a prepaid connection to a mobile network. Instead of a monthly bill, you load credit in advance, either as a plain balance or as a bundle of minutes, texts and data. When the credit is used up, the service pauses until you top up again. There is no minimum term, so you can walk away at any point.
Because nothing is billed after the event, prepaid SIMs are popular with people who want a firm limit on spending, with parents setting up a first phone for a child, and with visitors who need a UK number for a few weeks. They also work well in a second handset kept for travel or work.
How do I choose the right UK network?
Start with coverage where you spend most of your time, then compare what each network includes for the way you actually use a phone. Heavy video streaming calls for a large data allowance, whereas ringing relatives overseas makes international rates more important. Price matters, but a bundle that fits your habits usually matters more.
- Coverage: every network publishes a postcode checker. Test your home, your workplace and the journeys you make regularly.
- International calls: Lycamobile and Lebara build their bundles around calls to other countries.
- Data: compare the allowance in each bundle and find out what happens once it runs out.
- Topping up: pick a network whose credit is easy to buy. Our top-up vouchers cover the main UK networks.
Should I choose a physical SIM or an eSIM?
A physical SIM is a small card that slides into the phone’s SIM tray. An eSIM is a digital profile that the phone downloads, usually by scanning a QR code, onto a chip already built into the handset. Both connect you to the same network. Which one suits you depends on whether your phone supports eSIM and how you prefer to set things up.
| Question | Physical SIM | eSIM |
|---|---|---|
| How does it reach me? | Posted by Royal Mail or DHL | Set up digitally, with no card to post |
| Which phones work? | Any unlocked phone with a SIM tray | Unlocked phones that support eSIM |
| What about a new handset? | Take the card out and put it in the new phone | Transfer or reinstall the profile using the network’s steps |
| What can go wrong? | The card can be lost or damaged | A full reset of the phone may delete the profile |
To find out whether your phone handles eSIM, look in its mobile network settings for an option such as Add eSIM. You can browse our UK eSIM range alongside the pay as you go SIM cards collection.
How do I set up a new pay as you go SIM?
Setting up involves four steps: order the SIM, make sure your phone is unlocked, insert the card, then add credit with a voucher for that network. When the phone shows the new network’s name and some signal bars, make a short call or send a text to confirm that the SIM is active and working.
- Order from our SIM cards section. Postage is priced by weight and starts at £2.95 within the UK, and our delivery information page covers sending SIMs abroad.
- Check that the phone accepts other networks. If it is locked, our unlock codes can open it up.
- Power the phone down, fit the SIM and switch it back on.
- Top up with a voucher for the same network, following the redemption method on the product page.
Can I keep my existing phone number?
Yes. In the UK you can take your number to a new network by requesting a PAC, short for Porting Authorisation Code. Text PAC to 65075 from the phone that currently holds the number, and your existing network replies with the code. Pass that code to your new network and it arranges the switch for you.
Keep the old SIM in the phone until the move has gone through, because the number stays with your old network until then. Leftover credit on the old account may not travel with the number, so use it up first if you can.
Will the SIM fit my phone?
Almost certainly. Most SIMs now arrive as a multi-size card that pops out to standard, micro or nano size, so a single card suits nearly any handset. Press out only the size your phone needs and keep the remaining frame safe, as it can help if you ever move the SIM to an older phone with a larger slot.
Can I return a SIM I do not need?
Unused physical items, SIM cards included, can be sent back within 14 days. A SIM that has been activated or topped up no longer counts as unused, so decide before you put it in a phone. Contact us with your order number before posting anything, and we will explain where to send it and what happens next.
Frequently asked questions
Do I need a credit check?
No. Pay as you go involves no contract, so there is nothing to check. You simply buy credit when you want it.
How do I check my balance?
Each network offers a balance number, an app and an online account. Your SIM pack explains which ones apply to your network.
Can I use a UK pay as you go SIM abroad?
Many networks allow roaming, but rates and rules vary and change. Check your network’s current terms before you travel, or look at our EU roaming SIM cards.
Does a prepaid SIM need to be used regularly?
Some networks disconnect a SIM that has gone unused for a long stretch. A small top-up or the odd call now and then keeps most numbers active, but check your network’s own policy.