What's a SIM card?
SIM stands for Subscriber Identity Module. It’s a small plastic card with a computer chip that slots into your phone, connecting you with your mobile network. Your SIM card holds a lot of information, including security details, the services you’ve got access to, and your phone number, plus text messages, emails, photos, and your contacts’ phone numbers too.
SIM cards come in different sizes: Standard, Micro and Nano. Once you’ve chosen your SIM-card deal, you’ll probably receive a Multi or Combi SIM, which gives you a choice of all three sizes. You pick the one that fits your mobile phone.
SIM cards are transferable. You can move them between devices, as long as they’re compatible and not locked to another network.
To find out whether your phone is locked, put the SIM card in. If you get a signal and can make a call, your phone is unlocked. If you can’t, your network can unlock it for you, but you may have to pay.
What's an eSIM?
eSIMs (the e stands for embedded) give you multiple profiles on one handset. This means you can use different lines at different times – for example, one for work and one for personal use. They each have their own number.
Rather than having a physical SIM card, you download an eSIM via an app or QR code. The GSMA, a trade association for mobile networks across the world, predicts that by 2025, 35% of smartphones will use eSIMs.
The downside of eSIMs is that they’re more difficult to switch to a new phone. You’ll need to go through the activation process again rather than simply putting a physical card into your new phone.
On the upside, eSIMs don’t cost any more than a physical SIM. You’ve also got a choice of network providers offering them. Try EE, Lyca Mobile, O2, Three, Virgin Mobile or Vodafone.
But beware: eSIM cards don’t work on all handsets. They’ve only been around for about a decade.
You’ll need a newer iPhone or Android phone, such as:
- Google Pixel 2 and upwards
- iPhone XR and upwards
- Samsung Galaxy S20 and upwards
- Sony Xperia 1 IV, Sony Xperia 10 IV, Sony Xperia 1 MK5 and Sony Xperia 10 MK5
Later models of Motorola, Huawei, Oppo and Rakuten also come with eSIM capabilities.
What are the advantages of a SIM only deal?
SIM only deals come with shorter contracts, from 30 days upwards, as well as Pay As You Go plans which are contract free.
You don’t have to make a long-term commitment and it’s quick and easy to switch to a new plan if a better offer comes along or your needs change. Your network provider may still want a month’s notice though.
You can pay for what you need
With SIM only contracts, customisable plans let you choose the number of minutes and texts and amount of data that works for you, including unlimited data. Some plans also come with EU roaming, so you can use your phone abroad. Or you can get plans with unlimited use of social apps and access to services such as Netflix or Prime Video that won’t count as part of your data usage.
You may also have 5G and Wi-Fi calling if your phone is compatible.
It’s easier to change providers
With a SIM only deal, you’re not locked into a particular network. If you’re not happy with your current network provider and you’re not tied into a 12-or 24-month contract, you can easily switch to another.
Upgrading your phone is easy
Want the latest handset? You don’t need to wait. As long as it’s compatible with your SIM, you can upgrade and your monthly payments won’t change.
You can keep your phone
You’ve set up all the apps, you like the way it works: if you don’t want to upgrade, a SIM only deal allows you to hang on to your existing model.
No credit check
If you’re worried about your credit rating or you’ve been turned down for a mobile contract elsewhere, many providers offer SIM only plans, no credit check required. They may need to do an ID check though.
If your credit rating isn’t looking good, a SIM only contract can improve it over time provided you don’t miss any payments.
What are the disadvantages of SIM only deals?
Here are a few of the potential SIM only downsides.
The upfront cost of buying a phone
If you don’t have a handset, you’ll need to buy one. If you love the latest tech, this could be an expensive business. You can pick up a budget smartphone for around £100. Top-of-the-range models are much more.
Your device might become obsolete
A series of SIM only deals increases the likelihood that your phone will date, stop working effectively and even put your data at risk.
You might need to unlock your phone
It’s been illegal for network providers to lock your phone since December 2021, but if you got your phone before then, it might need to be unlocked. This can be a complicated process and comes with a fee.
How to get the best SIM only deals
The best SIM only deal for you isn’t just about price. It’ll be the one that ticks all your boxes for flexibility and what’s included in the package too.
An online comparison service can flag up the best SIM only deals that also match your specific criteria. Here are a few questions to help you decide on the best SIM card only deal for you. On a monthly basis:
- How much data do you use?
- How many minutes do you need?
- How many texts do you usually send?
- What kind of download speeds are you looking for?
- Do you want a pay-as-you-go SIM or a 30-day, 12-month or 24-month contract? A longer-term contract is likely to be cheaper, but a monthly SIM gives you more flexibility to switch to different network providers or tariffs.
- Do you travel a lot – and if so, where do you go? EU roaming and beyond is often included.
If you’re not sure about your average monthly usage, you can look at your mobile phone bills.
Look out for the freebies and extra perks that often come with mobile SIM only deals too. These include priority gig tickets and free music downloads, as well as broadband deals and 5G at no extra cost. Just make sure your smartphone is 5G enabled and you’ve got coverage in your area.
To see if you can get 5G where you live, put your postcode into Ofcom’s coverage checker.
Which SIM only deals include data roaming?
Data roaming allows you to use data abroad. Some SIM only deals include roaming in certain countries in the EU and beyond.
You can get SIM only deals with EU roaming included from iD Mobile, Lebara, Lyca Mobile, O2, SMARTY, and Talkmobile.
This means most calls, texts and data usage are charged at the same rate you’d pay at home and come out of your usual allowance. But always check the details of the deal and what countries it covers.
You may also have the option to buy a data bundle for the country you’re going to.
For SIM only deals on a rolling monthly contract, you can plan ahead and change your allowance if you’re going to be away for longer.
If you’re on a 12- or 24-month SIM only contract which doesn’t include a good deal on data roaming, getting a temporary physical SIM may be your next best option. Alternatively, you can upload an eSIM if it’s compatible with your smartphone.
This allows you to access data roaming offers from other providers which may be cheaper than what you usually get. The downside is that you’ll have a different mobile number while you’re away.
If you’re a regular traveller – although you still spend most of your time in the UK – it pays to compare offers for the best-value SIM only deal with the roaming add-on you need.
Unsure how much monthly
data you need?
Our mobile data usage calculator can help. From 100MB to 10GB,
find out how far your data package will get you.
You might also be interested in:
Previously, most mobile networks raised contract prices in line with inflation. From January 2025, however, Ofcom will ban inflation-based price hikes on new contracts, requiring future increases to be fixed and clearly stated upfront.
Confused services are provided at no cost to you, but we may receive a commission from the companies we refer you to. This helps to keep our site free for you to use. Learn more about how our site works.
*Switching from an ending 24-month handset contract to a SIM only contract (and keeping your existing handset) could save you £351 (£350.95) per year, or £29.25 per month. This calculation is based on the price of the top selling 24 month handset package in January 2023 (Apple iPhone 14 with 100GB data) against the cheapest equivalent SIM only deal on the Uswitch site as of January 2025 (TalkMobile 100GB data £9.95 per month on average ). Correct as of 30th January 2025.
cookie usage