What is a SIM only deal?

Key takeaways

• A SIM only deal is a mobile plan with calls, texts and data but no phone. You get a SIM or eSIM and use it in a phone you already own.
• SIM only deals usually run for 1 month, 12 months or 24 months. The monthly price is generally lower than a phone contract because you don't have to pay off a phone.
• Before signing, check the contract length, what leaving early costs, whether the price can rise mid-contract, and whether there’s a credit check.

 

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Your phone contract is almost up. The phone still works, the screen is only slightly cracked, and you're not ready to say goodbye. Then the email arrives asking whether you'd like to upgrade.

You don't have to. A SIM-only deal lets you keep the phone and change the plan. The idea is simple, but the jargon around it isn't always, so here's what it means, how it works and what to check before you sign up.

What is a SIM only deal?

A SIM only deal is a mobile plan that gives you calls, texts and data without a phone. You get a SIM card or an eSIM and use it in a phonet you already own.

You'll also see it called a SIM-only plan or a SIM-only contract. They all mean the same thing: airtime without the phone.

An eSIM is a digital SIM built into your phone, so there's nothing to pop in. We cover it in more detail in "What is an eSIM and how does it work?"

Because there's no phone in the price, there's no phone repayments either. That's the main reason SIM only deals are cheaper than a phone contract.

How does a SIM only deal work?

It works like any other mobile plan, minus the phone.

1. Pick a plan. Choose the data, minutes and texts you need, and how long you want to commit for.
2. Get your SIM. A physical SIM arrives in the post, or you set up an eSIM on a compatible phone.
3. Put it in your phone. Swap the SIM in, or follow the eSIM set-up steps, then activate it.
4. Pay monthly. You pay a set price each month for a set allowance of data, minutes and texts.

Because the SIM isn't tied to a phone, you can change phones whenever you like and keep the same plan.

How long does a SIM-only deal last?

Length is the key decision. Most UK providers offer three options.

Length	What to expect
1 month (rolling)	A rolling 1 month SIM only plan renews every month, so you can usually change or cancel it without waiting for a minimum term to end.
12 months	A 12 month SIM only deal fixes the price for a year. It may be cheaper each month than a rolling plan, but it commits you until the year is up.
24 months	A 24 month SIM only deal fixes the price for two years. It may offer the lowest monthly price, but it's the hardest to leave if a better deal turns up.

Longer isn't automatically better. A fixed term can mean a lower monthly price, but you pay for it in flexibility. If the saving is small, a rolling plan is usually the safer option: similar cost, and you can leave when something better turns up.

The small print worth checking

Before choosing a SIM-only plan, watch out for these four things.

Leaving early

If you leave before a fixed term ends, you may have to pay an early termination charge. You can check where you stand by texting INFO to 85075. Once you've switched, your old provider can't charge notice period fees after your switch date, according to Ofcom.

Price rises

Since 17 January 2025, providers can't include inflation-linked price increases in new contracts. Any increase must be stated as a fixed amount in pounds and pence, as Ofcom explains.

Credit checks

Whether a credit check is required depends on the provider and the contract length. 12- and 24-month deals often involve one, while some rolling monthly plans don't.

A credit check is how a provider assesses whether you'll pay a bill later. Plans paid in advance don't need one, which is how SMARTY's SIM-only deals work, so there's no credit check.

When the term ends

Some plans continue month to month on the same terms once the minimum term is over. When yours is nearly up, it's worth checking whether a different plan would suit you better.

Can you keep your number with a SIM only deal?

Yes. UK rules let you take your number with you when you switch.

1. From the phone with the number you want to keep, text PAC to 65075.
2. Your current provider sends a code. It should arrive within a minute and stays valid for 30 days.
3. Give the code to your new provider when you sign up.
4. The switch should be completed within one working day, and any gap in service shouldn't be longer than that.

Already cancelled? You can usually still ask for a code within a month.

Where SMARTY fits in

A lot of the faff in this guide comes from long contracts. With SMARTY, plans roll monthly, so there's no minimum term to get stuck in, and you can change or cancel whenever you like. There's no credit check, no annual price rises on rolling monthly plans. Every plan includes a free SIM, or an eSIM if your phone supports it. You can keep your number when you switch, too.

The latest details are on our SIM-only plans page.

FAQs

1. What does SIM only mean?

SIM only means paying for a mobile plan with calls, texts and data, but no phone included. You put the SIM or eSIM into a phone you already own.

2. Is a SIM only deal cheaper than a phone contract?

Usually, a SIM only deal doesn't include the cost of a phone. Exact savings depend on the plan, so compare the monthly price with what a phone contract would cost.

3. Do SIM only deals need a credit check?

It depends on the provider and the contract length. 12- and 24-month deals often involve a credit check, while some rolling monthly plans, including SMARTY's, don’t.