A SIM only deal gives you calls, texts and data without a phone. You keep your current handset, or buy one separately, and pay only for the plan.
That usually costs less than a phone contract. Ofcom has found that buying a handset and airtime together from one provider can be significantly more expensive than a SIM only plan with a separately bought phone. SIM only plans now make up half of all pay monthly mobile subscriptions in the UK.
This guide explains how they work, which contract length suits you and what to check before you order. When you are ready, choose the SIM only tab on our mobile deals comparison to filter by network, data and monthly cost.
What a SIM only plan includes
You get a SIM or eSIM and a monthly allowance of data, minutes and texts. Most plans include unlimited UK calls and texts, so data is the main difference between them. Most plans now include 5G at no extra charge, but you need a 5G phone and a network that reaches your area.
SIM only suits you if you already own your phone, buy handsets outright or have finished a phone contract. If you are still inside a phone contract, the handset and plan are bundled, so you usually cannot move to SIM only until the minimum term ends. Our guide to phone contracts covers that route, and buying a phone outright or on contract shows how to compare the total cost.
SIM only contract lengths
| Length | How it works | Who it suits |
|---|---|---|
| 30 day rolling | The plan renews each month. You leave by giving 30 days’ notice. | People who want flexibility, want to try a network or may move soon. |
| 12 month | Fixed for a year. Leaving early usually means paying the rest of the plan. | People who will stay for a year and want a steady plan. |
| 18 month | Offered by a few providers. The same exit rules apply. | People who have found a plan they are happy to keep for longer. |
| 24 month | The longest commitment. Planned yearly rises can apply. | People who will not change network and have checked the full terms. |
A 30 day plan is not pay as you go. You pay a set amount each month and your allowance renews automatically. Our pay as you go SIM guide covers top up SIMs.
Check your phone works with the plan
Three things can stop a new SIM working as you expect.
- Locked phones. Since December 2021, networks cannot sell locked phones. An older phone may still be locked to the network that supplied it. Ask that network for an unlock code, which is usually free, and do it before you switch.
- Older phones. All four networks have now switched off 3G, so a very old handset needs to support 4G calling to make calls reliably. Ofcom says most customers already have 4G phones.
- eSIM. If you want an eSIM, check that your phone supports it and that the provider offers it on the plan you pick. Some providers offer it only on selected plans. Our eSIM guide explains the setup.
Choose the right amount of data
Ofcom’s 2026 report put average use at 11.8GB a month per mobile data user in 2025. Your own figure may be well below that if you are on Wi-Fi at home and work. Check your phone’s settings for last month’s use before you choose, and avoid paying for far more than you need.
Unlimited data makes sense if you stream or use your phone as a hotspot without much Wi-Fi. Some unlimited plans limit the download speed, so read the terms. Some providers roll unused data into the next month. Our guide to how much mobile data you need helps you set the right level.
Pick a network that works where you live
EE, O2, Vodafone and Three own the masts. Vodafone and Three merged in 2025 and are combining their networks, while their consumer brands remain separate. Smaller brands use one of the four, so they share its coverage.
| Network | Brands that use it |
|---|---|
| EE | BT Mobile, Plusnet Mobile, Lycamobile, Utility Warehouse, Your Co-op, 1p Mobile, Ecotalk |
| O2 | giffgaff, Sky Mobile, Tesco Mobile |
| Vodafone | Lebara, Asda Mobile, Talkmobile, VOXI |
| Three | iD Mobile, Smarty, FreedomPop, Superdrug Mobile |
This list follows the one Ofcom publishes with its coverage checker. Brands can change host network, so confirm with the provider before you order.
Check coverage at your home and work postcode with Ofcom’s checker. It predicts indoor and outdoor coverage in 100 metre squares for all four networks, and shows outdoor 5G. These are predictions, not guarantees, so Ofcom also suggests asking people nearby which network works for them. Ofcom’s Map Your Mobile tool compares coverage and performance in your area. Our guides to mobile coverage, the best mobile networks and cheap mobile networks go further.
Other things to check before you order
- Introductory prices. Some plans start at a lower price for the first few months, then rise. Add up the full cost over the contract, not just the first month.
- Roaming. Allowances differ a lot. Some plans include a set amount in dozens of countries and others include none. See using your phone abroad.
- Credit checks. Fixed term plans usually involve one. Rolling plans vary by provider, and some use a soft check that confirms your identity and does not usually affect your score. Ask before you apply, and read our guide to mobile credit checks if you are worried.
Price rises and leaving early
Since 17 January 2025, providers must show any planned price rise in pounds and pence before you sign up. Rises still happen, so check the figure on the deal page. If a provider raises your price by more than you agreed, you can leave without a penalty within 30 days of being told. Ofcom pointed O2 customers to this right in 2026, after the network raised its April rise above the figure in their contracts. Our guide to mobile price rises explains how to check your own contract.
If you leave a fixed term plan early for another reason, you usually pay the remaining monthly charges. Text INFO to 85075 to see any charges for free, without starting a switch. Ofcom also bans providers from charging notice periods that run after your switch date.
Keep your number when you switch
- Text PAC to 65075 from the SIM you want to keep. Your provider replies within a minute with a code.
- Give the code to your new provider when you order.
- The new provider moves your number, normally within one working day.
- Your old plan ends at the same time, so you should not pay both.
Full steps are in our guide to switching mobile provider.
Ready to compare?
Use the SIM only tab on our mobile deals comparison to filter by network, data and monthly cost. Read the final price and terms on the provider’s page before you pay.
FAQs
What happens when my SIM only contract ends?
Your provider must tell you between 10 and 40 days before the minimum term ends, and show you its best deals. If you stay out of contract, it must send you best deal information at least once a year. Ofcom’s 2026 pricing report found that many customers pay more than they need to by staying out of contract.
How long does a PAC code last?
It lasts 30 days. If it runs out, text 65075 again. If you have several numbers on one account, such as a family plan, you cannot get codes by text and must ask online or by phone.
Can I use a SIM only plan in a tablet?
Only if the tablet has a SIM slot or supports eSIM, and many tablets are Wi-Fi only. Check the device first. For home internet over a mobile signal, see our guide to 5G and mobile broadband.