SIM Only Deals in the UK (No Contract, 2026 Buyer’s Guide)
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SIM only deals let you use your existing phone without paying for a new handset. Instead, you're paying for your mobile service, including data, calls and texts.
They're a great option if you already own a smartphone, want to avoid a long handset contract or simply want more flexibility over how much you spend.
This buyer's guide looks at some of the best SIM only options available in the UK in 2026 and explains how to choose the right SIM for your data usage and budget.
What Is a SIM Only Deal?
A SIM only deal provides mobile service without including a new phone. Simply insert a compatible SIM into your existing unlocked handset and use the included data, calls and texts.
Benefits of SIM only can include:
- Keep using your existing smartphone
- Avoid paying for another handset
- Flexible no-contract and PAYG options available
- Choose a data allowance that suits your usage
- Easy option for secondary or spare phones
PAYG vs Rolling SIM Only
Not every SIM only option works in the same way. Two common choices are preloaded PAYG SIMs and rolling SIM only plans.
| Type | Best For | How It Works |
|---|---|---|
| Preloaded PAYG | Flexible or short-term use | Includes a set allowance that's available for a specified period |
| Rolling SIM Only | Regular everyday use | Service continues on a recurring basis until cancelled, subject to the plan terms |
The best choice depends on whether you want an ongoing mobile service or simply need a set allowance without committing to a traditional handset contract.
Best SIM Only Deals to Buy Right Now
Best Flexible SIM – SMARTY No Contract SIM
The SMARTY SIM Card is a flexible option for users who want a no-contract SIM with access to 4G and 5G mobile data.
- No long-term contract
- 5G ready
- Flexible monthly plan options
- Works with compatible unlocked phones
- Also suitable for compatible tablets and mobile WiFi devices
Best Value SIM – Three 40GB PAYG SIM Pack
At £10, the Three 40GB PAYG SIM Pack offers a useful amount of data for everyday smartphone use without requiring a long-term contract.
- 40GB preloaded data
- Unlimited UK calls and texts
- One-month data pack
- 4G and 5G compatible
- No long-term contract
- Great for browsing, messaging and social media
View Three 40GB PAYG SIM – £10
Best Everyday SIM – Three 100GB PAYG SIM Pack
The Three 100GB PAYG SIM Pack gives you considerably more mobile data for £15, making it a strong middle ground for users who regularly stream, browse and use social media.
- 100GB preloaded data
- Unlimited UK calls and texts
- One-month data pack
- 4G and 5G compatible
- No long-term contract
- Ideal for regular mobile data users
View Three 100GB PAYG SIM – £15
Best High-Data SIM – Three 200GB PAYG SIM Pack
If you use a lot of mobile data but don't necessarily need unlimited data, the Three 200GB PAYG SIM Pack offers a generous allowance for £20.
- 200GB preloaded data
- Unlimited UK calls and texts
- One-month data pack
- 4G and 5G compatible
- No long-term contract
- Ideal for frequent streaming and heavy mobile use
View Three 200GB PAYG SIM – £20
Best Unlimited Data SIM – Three Unlimited PAYG SIM Pack
For very heavy mobile data users, the Three Unlimited PAYG SIM Pack removes the need to keep track of a fixed data allowance.
- Unlimited data
- Unlimited UK calls and texts
- PAYG flexibility
- No long-term contract
- Ideal for very heavy smartphone data usage
View Three Unlimited PAYG SIM – £35
How Much Mobile Data Do You Need?
Choosing the right data allowance can help you avoid paying for data you don't use while still giving you enough for your normal activities.
| Typical Usage | Suggested Option |
|---|---|
| Messaging, browsing and light social media | 40GB |
| Regular social media, music and video streaming | 100GB |
| Heavy streaming and frequent mobile data use | 200GB |
| Very heavy usage without monitoring a fixed allowance | Unlimited |
These are general recommendations rather than fixed rules. Your actual usage can vary considerably depending on streaming quality, apps and how often you're connected to WiFi.
What Should You Look for in a SIM Only Deal?
Data Allowance
Check how much mobile data you normally use before choosing a SIM. There's little benefit in choosing unlimited data if you regularly use only a small amount.
Calls and Texts
Many SIM options include generous or unlimited UK calls and texts, but always check the individual product before purchasing.
4G & 5G Access
If you have a 5G smartphone, choose a compatible SIM to take advantage of 5G where coverage is available. You'll need both a compatible device and suitable network coverage.
Validity and Renewal
Check whether you're buying a preloaded PAYG SIM with an allowance valid for a specific period or an ongoing rolling plan. They're different products even though neither includes a handset.
Network Coverage
Coverage can vary depending on your location. Check the network's coverage in the places where you'll use your phone most frequently before choosing your SIM.
Can You Keep Your Existing Mobile Number?
In most cases, yes. If you're moving from another UK mobile network, you can usually request a PAC (Porting Authorisation Code) from your existing provider and use it to transfer your mobile number to your new network.
Check the instructions from your new provider before starting the transfer.
Can You Use SIM Only with Any Phone?
A SIM only option can generally be used with a compatible unlocked phone. You should check that your handset supports the network and SIM type you're planning to use.
If you're buying a new handset at the same time, you can also pair your chosen SIM with one of the smartphones available from eFones.
What About Travel and Mobile Broadband SIMs?
Not every SIM is designed primarily for everyday smartphone use.
If you're travelling abroad, a travel SIM with a preloaded roaming allowance may be more suitable. If you're connecting a tablet, 4G/5G router or portable WiFi hotspot, consider a SIM suitable for mobile broadband use.
eFones also stocks dedicated Three Travel SIM options with different roaming allowances and validity periods.
Frequently Asked Questions
Do SIM only deals work with any phone?
They work with compatible devices. If you're changing networks, using an unlocked phone generally gives you the greatest flexibility.
Can I keep my existing phone number?
Usually, yes. UK customers can normally transfer their existing number to a new network using a PAC code.
Is SIM only cheaper than buying a phone contract?
If you already own a suitable smartphone, SIM only can be a cost-effective option because you aren't also paying for a new handset as part of the deal.
What's the difference between PAYG and SIM only?
SIM only means you're buying mobile service without a handset. PAYG is one way that service can be provided, while other SIM only options may operate on a recurring basis.
Can I get 5G with a SIM only deal?
Many current SIM options support 5G, but you'll need a compatible 5G smartphone and suitable network coverage. Check the individual SIM details before purchasing.
Can I use my SIM abroad?
Roaming availability, allowances and charges depend on the network and specific SIM. Always check the roaming terms and included destinations before travelling.
Shop SIM Only Deals at eFones
Whether you're looking for an affordable everyday SIM, a high-data option or unlimited data, explore the latest SIM cards available from eFones.