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What is a SIM only deal? Here’s everything you need to know before signing up

Finding the right one can save you a mound of money, but what is a SIM only deal and what should you look out for?

Nowadays, mobile networks like to throw around lots of statistics to grab your attention, with many even chucking in extra freebies to entice you onto one of their SIM plans. But let’s get back to basics: what is a SIM only deal, and why should you choose one?

To help, we’ve put together a brief explanation of the fundamentals, followed by bite-size sections that explain the key aspects of a SIM only deal. Along the way, we’ll also be recommending specific deals to save you time, whether you’re a Netflix addict, social media fiend, occasional browser or serious mobile gamer.

Read on to find out how to slash your monthly bill.

READ NEXT: The best PAYG SIM deals on the market

What is a SIM only deal?

Boiled down, a SIM only deal gets you a SIM card loaded with a set amount of data, calls and texts, which you then pay for on a monthly basis for, usually, one month, one year or two years.

You then insert the SIM into your existing phone to begin browsing and nattering. However, there’s a huge range of data allowances, data types (4G or 5G), download speeds, roaming charges and other extras to get your head around.

What should you look out for?

Mobile network

Some mobile providers are simply better than others: what might seem like a spectacular SIM only deal could end up getting you patchy coverage or ambivalent customer service. To sort the wheat from the chaff, Expert Reviews conducts a survey every year to compile our Mobile Network Awards.

In 2021, there was a clear winner: Sky Mobile, which piggybacks on O2’s network as a mobile virtual network operator (MVNO). It doesn’t have a vast number of one-year SIM only plans, but its customer service is unrivalled, it’s excellent value for money and it’s reliable. In short, it’s an unrivalled all-rounder.

That said, we’re also big fans of cost-effective Giffgaff, blisteringly fast EE, family-focused Tesco Mobile, ultra-cheap iD Mobile and Vodafone for its bundles. Honourable mentions should also go to Smarty, Voxi and Three for their SIM only selections, as well as Lebara for international calling.

Browse Sky Mobile’s SIM only deals

Direct or third party?

Before you start to consider factors such as contract length and data allowance, it’s worth comparing the SIM only deals directly from mobile networks with those that come via a third-party site.

The benefit of going direct is that you’ll often be treated to generous freebies and reductions. For instance, Three is currently offering a massive £100 prepaid Mastercard and six months half price when you sign up for its two-year unlimited data deal.

Third-party sites such as and Affordable Mobiles, on the other hand, serve up the cheapest prices and let you easily compare plans from the various providers. For instance, you can pick up a year of unlimited Three data for a staggering £8/mth via Affordable Mobiles. The downside is that the savings are often via automatic or manual cashback, with the latter involving sending a copy of your phone bill to claim the discount.

Browse’s SIM only deals


The amount of monthly data you need will depend entirely on how you use your phone. If you only do a bit of browsing or use Google Maps outside of the house, 5GB to 10GB should be more than enough. 8GB will set you back an eye-catching £9/mth from Sky Mobile.

However, if you regularly listen to Spotify or watch Netflix on your morning commute, it might be worth stepping up to a 25GB to 50GB plan for peace of mind. iD Mobile, for example, has a 30GB option for just £10/mth on a one or two-year contract.

At the far end of the spectrum are the 100GB, 250GB and unlimited SIM only deals. These are tailor-made for serial streamers, social media devotees, frequent downloaders and mobile gaming fanatics. They’re also handy if you’re planning to use your smartphone as a hotspot for your laptop. A good example is EE’s 150GB plan for £25/mth, which is often boosted to 160GB for no extra outlay.

There’s an exception to these rules: Voxi. This offshoot of Vodafone offers free social media usage and unlimited video-watching, alongside a monthly allowance of data. If you spend most of your screen time on TikTok, Instagram or Twitter, Voxi’s plans are well worth exploring.

Browse EE’s SIM only deals

Texts and minutes

The days of having to borrow someone else’s phone because you’d run out of minutes are long gone. The vast majority of SIM only deals now come with unlimited UK minutes and texts as standard. Even if one doesn’t, the allowance is likely to be more than you’ll ever use.

That’s certainly not the case with international calls, but, as you’ll see further down the page, there are still plenty of affordable SIM only options for ringing or texting friends and family in the EU, US, Australia, India, Nigeria, China and many others.

Note that you can also pick up “data-only” SIMs, which are perfect for tablets, dongles and phones that moonlight as hotspots. Smarty recently released a range of attention-grabbing options that each last for a month.

Browse Smarty’s SIM only deals

Contract length

SIM only deals normally last for one month, one year or two years, which each have their pros and cons. A one-month plan from, say, Giffgaff offers the ability to cancel at any time for free, with the caveat that 30-day contracts tend to be more expensive.

One-year deals, conversely, tie you in for a much longer period of time, but will be a lot cheaper. To use EE as an example, a one-month 100GB SIM is £34/mth, while the one-year rate for the same amount of data is £29/mth.

However, the biggest savings come with two-year contracts. Although some users might be put off by being tied down for so long, they’re even cheaper. Take Vodafone: a year of unlimited 5G data is £35/mth, while the two-year equivalent is £32/mth.

Browse Vodafone’s SIM only deals


Which brings us to the most important factor for most SIM seekers: the price. As we mentioned above, the best option for those on a budget is iD Mobile, but that doesn’t mean that you can’t pick up bargains from the other networks.

To help, we’ve put together a list of the best SIM only deals on the market, which we update on a regular basis. Our roundup of the best pay-as-you-go deals is also worth a look.

Browse iD Mobile’s SIM only deals


Switching from one network to another once your contract has ended has never been easier – transferring your number is now just a case of entering a PAC code and waiting. However, be aware that you’ll incur costs by ending your plan early, meaning you’re better off going for a shorter deal if you like to shop around.

Networks offer rewards for brand-new customers too, with the best at the moment being Three’s £100 gift card for switchers.

Browse Three’s SIM only deals

Download speeds

5G promises blisteringly fast download speeds to compatible phones and dozens of urban areas across the UK are now covered, but that still leaves huge swathes of the country relying on 4G. Consequently, it’s worth checking if you’re able to get the fastest speeds before buying – there’s no point in paying for a service that you can’t access.

But which network is fastest? Lots of different companies conduct tests, each posting a slightly different set of results. Nevertheless, a broad pattern emerges: EE consistently serves up the fastest 4G and 5G speeds by far, followed by Three, O2 and Vodafone – although not always in that order. The downside is that EE tends to offer the most expensive SIM only plans.

Browse EE’s SIM only deals

Roaming charges

Once upon a time, you could use your SIM in the EU for no extra charge, but Brexit means that hefty roaming charges now apply – with the notable exception of O2. Naturally, those become even pricier if you’re heading further afield to countries such as the US, Australia or India.

In that case, you should peruse the SIM only deals from the likes of Lebara and Lycamobile, which will not only let you browse on your travels without worrying about astronomic charges, but also include generous allowances for calling and texting phones around the world.

Browse Lycamobile’s SIM only deals

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