Last updated: Thursday 17 September 2026 (Europe/London).
Next update: when SMARTY reprints its Data Only Price Guide or Three changes PAYG data-pack cash on three.co.uk.
By: Switch Editorial Team, Switch Squid Ltd
As of 17 September 2026, the cheapest verified always-on monthly data-only SIM we opened on a retailer’s own site is SMARTY’s 2GB Data Only plan at £5 a month (£60 over 12 months). If you only need a tablet or MiFi occasionally, Three’s PAYG 120GB pack at £40 for 12 months (£3.33/month effective) undercuts every rolling monthly data-only tier we checked — but you must use the allowance within the pack’s validity window.
I am Switch. This page answers data only SIM UK cheapest for tablet, MiFi, dongle and hotspot intent — not phone call+text SIMs dressed up as “data deals”. Cash leads below come from SMARTY’s published Price Guide / data-sim shop and Three’s own data-sim PAYG page today. Soft context on the mobile hub is fine; Get deal buttons use Awin affiliate deepLinks (aff 911601), never an own-hub Compare as the primary CTA.
Get deal — live SIM-only cards →
What “data only” actually means
A data-only SIM sells a data allowance without inclusive UK minutes and texts. It is designed for tablets, MiFi hotspots, USB dongles and laptop eSIM slots where you never dial a number. It is not automatically cheaper than a normal SIM: MoneySavingExpert and every cash table we run keep showing that call+text SIMs often win on £ per GB because networks price voice/SMS as near-zero and compete hardest on smartphone plans.
Use a data-only product when your device cannot use minutes usefully, when your network’s data-only SKU is the only unlocked hotspot path, or when you want a separate allowance so the family phone plan stays clean. Otherwise buy a cheap rolling phone SIM and put it in the tablet — that is often the lower 12-month cash path.
Verified cash table (17 Sep 2026)
| Retailer / product | Allowance | Cash | Term / validity | 12-month equivalent | Network |
|---|---|---|---|---|---|
| SMARTY Data Only | 2GB | £5/mo | 1-month rolling | £60 | Three |
| SMARTY Data Only | 15GB | £9/mo | 1-month rolling | £108 | Three |
| SMARTY Data Only | 40GB | £13/mo | 1-month rolling | £156 | Three |
| SMARTY Data Only | 100GB | £17/mo | 1-month rolling | £204 | Three |
| SMARTY Data Only | Unlimited | £20/mo | 1-month rolling | £240 | Three |
| Three PAYG Data Only | 10GB | £10 | 1 month pack | £120 if renewed monthly | Three |
| Three PAYG Data Only | 15GB | £20 | 3 months pack | £80 if repeated | Three |
| Three PAYG Data Only | 50GB | £60 | 12 months pack | £60 | Three |
| Three PAYG Data Only | 120GB | £40 | 12 months pack | £40 (best occasional) | Three |
Sources: SMARTY Price Guide PDF + smarty.co.uk/data-sim; three.co.uk/sim/data-sim-payg — all opened 17 September 2026. Prices include VAT as shown by the retailers. Promotions change; re-check the shop before you pay.
Get deal — compare live SIM cards →
How to choose: monthly vs long pack
Always-on tablet / WFH hotspot: SMARTY’s rolling Data Only ladder is the cleanest public monthly grid. Start at 2GB (£5) if you only sync email and light browsing; jump to 15GB (£9) or 40GB (£13) if you hotspot a laptop. Unlimited at £20 is the ceiling when you refuse to count GB.
Travel MiFi / holiday house / spare router: Three’s 120GB for £40 over 12 months is the cash winner if you will actually use the pack across the year. Do not buy it if you will burn 120GB in two months of 4K streaming — then a monthly Unlimited SMARTY plan is more honest.
EU roaming: SMARTY’s Price Guide applies a 12GB fair-use style EU data treatment on Data Only plans (calls/texts out of plan). Three PAYG data packs list pack-specific roaming allowances on the product page — read the pack you buy, not a phone-plan Go Roam marketing tile.
Networks we checked but did not lead with cash
iD Mobile, Talkmobile, Lebara, EE, O2 and Vodafone all sell SIM products that can sit in tablets. Dedicated public “data only” ladders with clear 12-month cash were not the lead story on their own shops in this research window the way SMARTY and Three were. Comparison sites sometimes list iD/Talkmobile data-only tiles — we do not reprint those until the retailer’s own checkout shows the same cash. That is SwitchSquid’s retailer-verified rule.
giffgaff remains a strong phone-SIM neighbour for light tablet use (goodybags include data + minutes), but it is not a dedicated data-only SKU in the sense of this URL.
Hotspotting, speed caps and fair use
SMARTY markets unrestricted hotspotting and no speed limits on Data Only plans on its data-sim page. Three markets 5G-capable PAYG data SIMs. Real-world speed still depends on mast load, indoor walls and whether your MiFi radio is 4G-only. A “unlimited” label never means infinite simultaneous 8K streams without congestion management — read the retailer’s fair-use wording before you promise the family a fibre replacement.
If you are replacing home broadband with a data SIM, run a week of real usage first. A 40GB plan looks fine until two kids stream after school. Full-fibre or fixed wireless will usually beat mobile on contention once you pass a few hundred GB — soft link: our broadband hub for fixed deals.
eSIM vs plastic for tablets
Many modern iPads and Android tablets take eSIM. SMARTY and Three both support eSIM journeys for eligible plans — confirm the exact Data Only / PAYG pack is eSIM-eligible in checkout, because not every legacy PAYG pack is. Plastic nano-SIM still wins for older MiFi routers that only have a tray.
Porting a phone number onto a data-only SIM is usually pointless: there is no inclusive minutes product to keep. Keep your voice number on a cheap phone SIM and run data-only as a second line.
Worked examples (illustrative)
- School tablet, weekends only: Three 50GB/12m at £60 or SMARTY 2GB monthly if usage is tiny.
- Van MiFi for deliveries: SMARTY 40GB £13/mo if you need continuous service; Three 120GB/£40 if annual mileage of data is modest.
- Backup when Virgin/Openreach dies: SMARTY Unlimited £20/mo you can pause after the outage — rolling terms matter here.
PAC, switching and keeping a number
Data-only SIMs rarely need a PAC. If you are moving a phone number, keep voice on a separate cheap SIM and treat the tablet line as a brand-new activation. Switching between SMARTY and Three PAYG is a cancel-and-buy journey, not One Touch Switch — mobile number porting rules still apply if you insist on moving an MSISDN onto a data SKU that accepts it.
Watch auto-renew on rolling SMARTY plans: if the tablet sits in a drawer for three months you will still pay unless you pause or cancel in the app. Three PAYG packs die when the validity ends — set a calendar reminder before the 12-month window closes if you still need service.
Security and public Wi-Fi
A personal data SIM beats café Wi-Fi for banking and work VPN sessions because you control the radio path. That does not remove malware risk on the device itself. Keep OS updates on, prefer eSIM where the tablet supports it (harder to steal than a tray SIM), and disable unnecessary hotspot sharing when you are not using it — an open personal hotspot is a gift to the next table.
For kids’ tablets, pair a low GB plan with content controls on the device rather than chasing Unlimited “so they never run out”. Running out is a feature when you want bedtime to stick.
FAQ
What is the cheapest data only SIM in the UK right now?
For a rolling monthly plan, SMARTY 2GB Data Only at £5/mo (£60/year) as of 17 Sep 2026. For a long pack, Three’s 120GB PAYG data SIM at £40 for 12 months is cheaper if that validity fits your use.
Are data-only SIMs cheaper than normal SIMs?
Often no. Phone SIMs with minutes/texts frequently undercut dedicated data-only £/GB. Compare both before you buy.
Can I put a data-only SIM in a phone?
Usually yes for data, but you will pay out-of-bundle rates for calls/texts. Buy a phone SIM if you need voice.
Does SMARTY Data Only allow hotspotting?
SMARTY’s data-sim page states unrestricted hotspotting on Data Only plans. Confirm in the live terms at purchase.
Is Three’s £40 / 120GB pack really 12 months?
Yes per three.co.uk/sim/data-sim-payg on 17 Sep 2026 — the pack lasts 12 months with the stated roaming notes on that page.
Which network is better for rural MiFi?
Coverage is mast-specific. SMARTY rides Three; try a short rolling plan before you commit a year of packs.
Do I need a credit check?
SMARTY Data Only and Three PAYG data packs are prepaid-style products — no traditional 24-month credit agreement. Always read the retailer’s eligibility copy.
Where should I buy?
Prefer the retailer’s own site or a live affiliate deepLink. SwitchSquid Get deal buttons use Awin campaign 911601.
Get deal — live data / SIM offers →
Retailer prices change. Affiliate links may earn SwitchSquid a commission at no extra cost to you.
