SIM Only Deals UK (2026)
Bring your own phone. From £8/month for unlimited calls & texts, £12 for unlimited data.
SIM-only is the single biggest saving most UK mobile users haven't made. The average UK phone+SIM contract costs £35-£55/month, while a SIM-only deal with the same network allowances costs £12-£20/month. Over a 24-month contract, that's a £500-£800 saving — enough to buy a decent phone outright and still come out ahead. Below: the best UK SIM-only deals in April 2026, how to switch without losing your number, and the differences between Big Four networks and MVNOs.
Cheapest UK SIM-only deals (April 2026)
| Provider | Price | Data | Network | Contract |
|---|---|---|---|---|
| Smarty | £8/mo | 15GB | Three | 1 month rolling |
| Smarty Unlimited | £12/mo | Unlimited | Three | 12 months |
| Voxi Endless | £15/mo | Unlimited | Vodafone | 1 month rolling |
| iD Mobile Unlimited | £16/mo | Unlimited | Three | 12 months |
| Lebara | £8/mo | 20GB | Vodafone | 1 month rolling |
| giffgaff Unlimited | £25/mo | Unlimited | O2 | 1 month rolling |
| Tesco Mobile | £9/mo | 12GB | O2 | 12 months |
| EE Smart 200GB | £22/mo | 200GB | EE (own) | 12 months |
Prices and terms as of April 2026. Always check the provider's website for current offers before switching.
How to switch to SIM-only
- Check your current contract end date — switching mid-contract may trigger early-exit fees.
- Text PAC to 65075 from the phone you want to transfer. You'll receive your Porting Authorisation Code within one minute.
- Order the new SIM from your chosen provider, giving them the PAC. Most SIMs arrive in 2-3 days; eSIMs are instant.
- Activate — your old number transfers within one business day. No gap in service.
Is your phone unlocked?
UK phones bought on contract since December 2021 are automatically unlocked under Ofcom rules. Older phones may be locked to the original network — contact them free of charge to request unlocking. eSIM-capable phones (iPhone XS and newer, Samsung S20+ and newer, Pixel 3 and newer) can activate SIM-only plans without a physical SIM.
Questions answered
A mobile contract that includes only a SIM card (calls, texts, data) with no handset. You bring your own phone, or buy one outright separately. SIM-only deals are cheaper than combined handset + airtime contracts because you're not financing a phone through the monthly bill.
Unlimited data, calls and texts SIM-only contracts in the UK start at £8-£15/month (Smarty, Voxi, iD Mobile, Lebara). Mid-tier deals with 100GB+ run £12-£20/month. Big network direct (Vodafone, O2, EE, Three) charge £18-£30/month for similar allowances.
1-month rolling: cancel or change anytime, typically 10-20% more expensive per GB. 12-month: locked in, cheaper per GB, but no flexibility. For most users, 12-month deals are cheaper unless you're travelling abroad long-term or unsure about your provider.
Yes. Request a PAC (Porting Authorisation Code) from your current provider by texting PAC to 65075 — Ofcom rules require them to send it within one minute. Give the PAC to your new provider and your number transfers within one business day.
Yes, if your phone is unlocked. Phones bought on contract since 2021 are automatically sold unlocked under Ofcom rules. Older handsets may be locked to a specific network — contact the original provider free of charge to unlock. eSIM-capable phones can activate digitally without a physical SIM.
Within the EU: most UK SIM-only deals still include roaming or a fair-use allowance after Brexit (e.g., Smarty up to 12GB, Vodafone Xtra at no extra cost). Outside the EU: roaming typically costs extra (£3-£7/day). Check the provider's roaming policy before travelling.
Most UK SIM-only plans now include 5G at no extra charge. Mid-band 5G (all four networks have it) gives 200-500 Mbps in cities — useful for tethering or heavy streaming. For most day-to-day usage, 4G is plenty.
As of April 2026: Smarty Unlimited £12/month (12-month), Voxi Unlimited £15/month, iD Mobile Unlimited £16/month. Lebara occasionally runs promotional unlimited deals at £10/month for new customers.
Directly: no — UK mobile data allowances are per-SIM. Indirectly: use your phone as a hotspot to share with other devices (SMARTY, Voxi, iD allow unlimited tethering). For multi-person data sharing, look at a home broadband plan instead, or O2/Vodafone's multi-SIM family plans.
MVNOs (Smarty on Three, Voxi on Vodafone, iD on Three, Lebara on Vodafone, Tesco Mobile on O2, giffgaff on O2) use the same network towers as the Big Four but charge 30-50% less. Potential downside: traffic may be de-prioritised during network congestion, which is imperceptible for most users. For the majority, an MVNO is the better deal.