Free SIM Card UK: How It Works and How to Switch

What a free SIM card is

A free SIM card in the UK is a pay as you go SIM that a mobile company sends or gives you without an upfront charge. You do not pay for the plastic or the delivery. Instead, you add credit or buy a monthly bundle, and you pay only for what you use. There is no credit check, so you can order one even if you have a thin credit file or no UK credit history. The SIM comes with a phone number and can be used in any unlocked handset.

This is different from a contract SIM, where you agree to pay a set amount each month for a minimum term. It is also different from a SIM-only deal, which is a monthly plan without a handset but still a recurring payment. A free SIM is the entry point: no commitment, no monthly bill unless you choose a bundle, and no early termination charge. The trade off is that pay as you go rates are usually higher per call, text or gigabyte than contract or SIM-only rates. Ofcom notes that pay as you go charges only for what is used, each call, text or gigabyte costs more, and it needs no credit check.

Pay as you go, SIM-only and contracts compared

Pay as you go is the most flexible option. You top up when you need to, and if you do not use the phone, you do not pay. There is no credit check and no minimum term. The downside is that the unit cost of calls, texts and data is higher than on a monthly plan. If you use your phone regularly, the total can exceed a SIM-only deal.

SIM-only deals are monthly plans that do not include a handset. Ofcom says SIM-only deals are usually cheaper than contracts that come with a phone, and terms are one month rolling, 12 months or 24 months. A one month rolling deal gives you the ability to leave with little notice, while a 12 or 24 month deal usually lowers the monthly price but locks you in. You need an unlocked phone to use a SIM-only deal, but since 17 December 2021 mobile companies in the UK have been banned from selling handsets locked to their network, so a phone bought new since then should accept any SIM.

Pay monthly contracts with a phone usually run 12, 18 or 24 months and can cost more in the long term than buying a phone separately plus a SIM-only deal. The handset cost is spread across the contract, and you may pay interest or a higher total than buying the phone outright. The advantage is that you get the phone immediately and pay monthly. The disadvantage is the commitment and the total cost. For a free SIM user, the comparison is simple: pay as you go for low or irregular use, SIM-only for regular use with your own phone, and a contract only if you need a new handset and accept the total cost.

Using a free SIM in your current phone

Most phones sold in the UK since 17 December 2021 are not locked to a network. That means you can put a free SIM from any provider into your current phone and it should work. If you have an older handset, it may be locked to the network that sold it. You can usually ask that network for an unlock code, sometimes for a fee, or use a third party unlocking service. Once unlocked, the phone will accept a free SIM from another provider.

Check the SIM size before ordering. SIMs come in standard, micro and nano sizes. Many free SIMs are supplied as a three in one punch out card that fits all sizes, but not all. If you order the wrong size, you may need an adapter or a replacement SIM. Also check that your phone supports the network frequencies used by the provider. In the UK, the main networks use similar bands, so a phone bought in the UK should work on any UK network. If you bought the phone abroad, check the bands before ordering.

When the free SIM arrives, insert it, turn the phone on, and follow the provider instructions to activate it. You may need to top up or buy a bundle before you can make calls or use data. Keep your old SIM safe until you are sure the new one works, especially if you plan to transfer your number.

Keeping your number: PAC and STAC codes

To keep your mobile number when switching, text PAC to 65075. This is the Ofcom switching code. The old provider must reply with your PAC and important information about any early termination charges. The PAC is valid for 30 days. Give it to the new provider when you sign up. The new provider must complete the switch within one working day. The old provider must not charge for any notice period after the switching date.

If you do not want to keep your number, text STAC to 75075. This gives you a switching authorisation code. You do not need to give a reason for leaving. The switch should also complete within one working day. A number can usually still be transferred within one month of cancelling the old service, so if you cancel first and change your mind, you may still be able to move the number.

Before you request a PAC, check your contract end date. If you are still in a minimum term, you may have to pay early termination charges. The PAC reply from your old provider will tell you if any apply. If you are on pay as you go, there is usually no early termination charge. Once the switch is complete, your old SIM will stop working and your number will be on the new SIM.

Costs to watch on pay as you go

Pay as you go looks cheap because there is no monthly bill, but the unit costs add up. Each call, text and gigabyte costs more than on a contract or SIM-only deal. If you use data heavily, a bundle may be better value than paying per gigabyte. Ofcom advice is to avoid unlimited data unless it is needed, check fair usage limits, use Wi-Fi and Wi-Fi Calling, and ask for a bill limit. A bill limit caps how much you can spend, which prevents a surprise from out of bundle charges.

Watch out for charges for calls to non geographic numbers, premium rate services, and international calls. These are not usually included in bundles. Also check the cost of MMS and picture messages, which are often excluded. If you travel abroad, check roaming charges. The UK left the EU, so roaming rules have changed. Some providers include EU roaming, others charge. Check before you travel.

If you are on Universal Credit, Pension Credit or certain other benefits, you may qualify for a mobile social tariff. These are cheaper plans offered by some providers. They are not free SIMs, but they can reduce your monthly cost. Ask your provider or check Ofcom information for social tariff eligibility.

Checklist before ordering a free SIM

Before you order a free SIM, check that your phone is unlocked. If it was bought new in the UK since 17 December 2021, it should be. If it is older, ask the original network for an unlock code. Check the SIM size your phone needs. Check that you have a PAC if you want to keep your number, or a STAC if you do not. Text PAC to 65075 or STAC to 75075 to get the code. The switch must complete within one working day.

Check the pay as you go rates for calls, texts and data. Compare the cost of a bundle with paying per unit. If you use a lot of data, a SIM-only deal may be cheaper than pay as you go. Ofcom says SIM-only deals are usually cheaper than contracts that come with a phone. If you need a new handset, compare the total cost of a contract with buying the phone separately plus a SIM-only deal.

Ask about a bill limit if you are worried about overspending. Check fair usage limits on any unlimited or large data bundle. Use Wi-Fi and Wi-Fi Calling where possible to reduce mobile data use. If you are on certain benefits, ask about social tariffs. Finally, keep your old SIM until the new one works and your number has transferred.

Source: Ofcom.

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Frequently asked questions

Is a free SIM card really free?

The SIM itself is free, with no upfront cost. You pay for calls, texts and data as you use them, or by buying a bundle. There is no credit check and no monthly bill unless you choose a recurring plan.

Can I keep my number when I switch to a free SIM?

Yes. Text PAC to 65075 to get your switching code. Give it to the new provider. The new provider must complete the switch within one working day. The old provider must not charge for any notice period after the switching date.

What if I do not want to keep my number?

Text STAC to 75075 to get a switching authorisation code. You do not need to give a reason for leaving. The switch should complete within one working day.

Will a free SIM work in my current phone?

If your phone was bought new in the UK since 17 December 2021, it should be unlocked and work with any UK network SIM. Older phones may be locked to the original network. You can ask that network for an unlock code.

Is pay as you go cheaper than a contract?

It depends on use. Pay as you go has no monthly commitment and no credit check, but each call, text or gigabyte costs more. Ofcom says SIM-only deals are usually cheaper than contracts that come with a phone. For low or irregular use, pay as you go can be cheaper.