What is a SIM-Only Deal?

How does a SIM-only deal work?

When you sign up for a SIM-only plan, the network sends you a physical SIM card to put in your phone, or you activate an eSIM directly on your device. Your phone then connects to that network and uses your monthly allowance for calls, texts, and data. At the end of each billing period, your allowance resets.

Most SIM-only deals are either 30-day rolling contracts or fixed 12 or 24-month contracts. On a 30-day plan, you can switch or cancel at any time with no exit fees. On a 12 or 24-month contract, you commit to a set price for the duration, which sometimes means a lower monthly cost but less flexibility to leave.

SIM-only vs pay monthly handset contracts

A pay monthly handset contract bundles a phone and a SIM plan together. You pay a higher monthly amount that covers both the cost of the handset and the network service. Once the contract ends, you have paid off the phone but your bill usually stays the same unless you upgrade or switch.

A SIM-only deal separates the two. You own your phone outright and pay only for the network service. This makes SIM-only consistently cheaper on a monthly basis. According to Ofcom's research, the average UK household could save significantly by switching to SIM-only once their handset contract ends rather than rolling onto the same deal.

SIM-only makes the most sense if your current phone is in good working order and you do not need to upgrade. If you do want a new phone, you can buy one outright at a time that suits you and pair it with a SIM-only plan, rather than being tied to a two-year contract cycle.

What is an eSIM?

An eSIM is a digital SIM built into your phone that does not require a physical card. Instead of waiting for a SIM to arrive in the post, you scan a QR code or follow an activation process in the network's app, and your phone is connected within minutes. Most modern smartphones support eSIMs, including recent iPhones, Samsung Galaxy devices, and Google Pixel phones.

Several networks on SIM Only Finder offer eSIM activation, including spusu, iD Mobile, and others. You can filter for eSIM-compatible deals on our deals pages.

How much data do I need?

According to Ofcom's Connected Nations report, the average UK mobile user consumes around 10.6GB of data per month. If you are mostly on Wi-Fi at home and work, you may need significantly less than this. If you stream video, use your phone as a hotspot, or spend a lot of time away from Wi-Fi, you may need more.

The easiest way to check is to look at your current phone's data usage in settings. Both iOS and Android show a breakdown of how much data you have used in the current period. Use this as your baseline when comparing plans.

If you are unsure, a 30-day rolling plan lets you start with one allowance and switch up or down the following month without any penalty.

How do I keep my existing number?

Keeping your number when switching to a SIM-only deal is straightforward. Text PAC to 65075 from your current phone. You will receive a PAC code by text within 60 seconds, free of charge. Give this code to your new network when you sign up, and your number will transfer automatically, usually within one working day. Your old plan cancels automatically when the transfer completes.

If you do not want to keep your number, you can simply activate your new SIM without providing a PAC code and you will be given a new number.

Do I need a credit check for a SIM-only deal?

It depends on the network and the contract length. Most 30-day rolling plans do not require a credit check, as you pay upfront each month. Some 12 and 24-month contracts may require one. Several networks, including spusu, iD Mobile, Smarty, and Lycamobile, offer plans with no credit check required. You can filter for no credit check SIM-only deals on our deals page.

Will my price go up mid-contract?

On most 12 and 24-month contracts with major networks, prices increase each April by a fixed amount stated at sign-up. This is required to be shown in pounds and pence under Ofcom rules introduced in January 2025. Some smaller networks, including spusu and Lycamobile, have committed to no price rises at all. For a full breakdown of which networks raise prices and by how much, see our guide to SIM-only mid-contract price rises.

On a 30-day rolling plan, your provider can still raise prices but you are free to leave at any time without penalty if they do.

FAQs

Can I use a SIM-only deal in any phone?

Yes, as long as your phone is unlocked. Phones sold in the UK after December 2021 must be sold unlocked by law. If you bought your phone before that date and it was locked to a specific network, contact your previous network to request an unlock, which is free of charge.

What is the difference between a 30-day and 12-month SIM-only deal?

A 30-day plan renews each month and can be cancelled or changed at any time. A 12-month plan locks in a price for a year, sometimes at a slightly lower monthly cost, but charges an exit fee if you leave early. If flexibility matters more than the lowest possible price, a 30-day plan is the safer choice.

Can I roam abroad on a SIM-only deal?

Many SIM-only plans include EU roaming as standard, meaning you can use your calls, texts, and data allowance in EU countries at no extra cost, subject to fair use limits. Networks including spusu, iD Mobile, Smarty, and Tesco Mobile all include EU roaming. Check the specific plan terms before travelling, as roaming allowances vary. See our guide to EU roaming fees for more detail.

What happens when my SIM-only contract ends?

On a 30-day plan, nothing changes — it continues rolling until you cancel. On a 12 or 24-month contract, it typically moves to a rolling monthly arrangement on the same terms. Networks are required to notify you before your contract ends so you can decide whether to renew, switch, or renegotiate.