A SIM-only plan in your own 4G or 5G router: the rules

The networks sell two different things over the same masts:

• 4G or 5G home broadband: sold for use at home, with a hub supplied by the provider. Three's Home Broadband terms call it "a domestic service" with indoor equipment "for use in your home at the address you have provided". EE describes its 4G and 5G home plans as "for mobile internet in a fixed location", with hubs for indoor use only.
• A SIM-only mobile plan: written for phones, tablets and other mobile devices. Its rules are about which devices you use and whether your use is personal, not about an address.

They aren't interchangeable. Three's Home Broadband terms say its Home Broadband SIM may only be used in equipment Three has authorised, and that using it in a mobile device is charged under a separate Mobile Broadband Price Guide. Our guide to whether 4G or 5G home broadband can replace a fixed line covers how those home plans work, and the deal pages for Three broadband, Vodafone broadband and EE broadband show what each sells for the home.

A summary of the wording on each network's own pages and terms documents. It isn't legal advice.

Personal use. Three, Vodafone, EE and SMARTY all limit their plans to personal use, and Three's and Vodafone's terms also ban reselling. Running a business through a phone SIM in a router risks breaching that. Whether a whole household sharing one SIM counts as personal use isn't spelled out; Vodafone's policy, for instance, talks about use by an individual.

Tethering means sharing a device's mobile data with other devices, and a router exists to do exactly that for many devices at once. Example (hypothetical): a family of four with phones, laptops, a smart TV and a console can easily pass 12 devices. If you're on EE terms with the 12-device line, that matters; if your terms are silent, ask.

Unlimited rarely means no rules. The points where a network may act differ: 200GB for two months running (Vodafone's traffic-management flag), 600GB a month (EE, and Vodafone's investigation point), or "excessive" use in Three's terms. What follows differs too, from slightly lower priority on busy cells to a move to another plan. To judge whether you'd come near those figures, see our guide to how much data home broadband uses.

Before buying a router or digging out an old one, check:

• It's unlocked. ISPreview reported that from 17 December 2021 Ofcom's rules mean mobile operators can no longer supply locked phones, but that report covers phones only. A router or dongle from a network may still be locked to it, so check before buying second-hand.
• It supports 4G or 5G. Three's terms say 3G-only devices no longer work on its network.
• It supports your network's frequencies. Ask the network which 4G and 5G bands it uses and check them against the router maker's specification.
• It takes your SIM. Check the slot size matches the card you'll get.
• 5G only helps where there's 5G. For the newer 5G Standalone, see 5G Standalone explained.

A router you bought is also yours to fix: iD staff said support for SIMs in unsupported devices would be limited, and Three's clause 5.3 disclaims responsibility for problems in unauthorised devices. Our guide to securing your home router and Wi-Fi covers passwords and updates.

Coverage varies between networks. Ofcom's Spring 2026 update (January 2026 data, as reported by ISPreview) put individual operators' outdoor 5G coverage at between 76% and 94% of UK premises, and outdoor 5G from all operators at 64%.

• Use the coverage checker of the network the SIM actually runs on: for an iD SIM, that's Three's.
• Check your address, then test where the router will sit. Three says its home broadband speeds can be affected by where the hub is placed, line of sight to the nearest mast, hills, how many people nearby are online, and the thickness of walls and windows. A router you bought faces the same physics.
• Test at different times of day, including the evening, with our broadband speed test.

In the countryside, our guide to the Shared Rural Network and rural 4G explains what that programme does and doesn't cover.

• Automatic compensation. Ofcom says its voluntary automatic compensation scheme covers residential fixed broadband and landline products, paying out for delayed repairs, missed engineer appointments and late starts. We found nothing saying it covers a mobile SIM plan, so don't count on it. Our guide to automatic compensation for broadband faults lists the providers signed up.
• A landline. A SIM in a router gives you data, not a home phone line. GOV.UK expects the move from analogue to digital landlines to be finished for most customers by January 2027, and warns that telecare devices on digital lines may stop working in a power cut without battery back-up. If anyone relies on a telecare alarm, read our guide to telecare and alarms on a digital landline first.
• Emergency calls. Three's terms warn that a SIM in a device it hasn't authorised may affect usage, "including making emergency calls". Keep a working mobile phone for 999.
• Router support. Expect to sort out faults yourself or with the router's maker.

If you need a home phone line too, broadband and phone deals are the more natural fit.

• A backup for when fixed broadband fails, which SMARTY markets its data SIMs for. Our guide to backup broadband connections covers the providers' own 4G backup products too.
• Somewhere that isn't a fixed home, such as a touring caravan or a boat, where an address-based plan may not fit. Three's Home Broadband terms describe equipment "for use in your home at the address you have provided", although its support page says you can take the hub wherever there's coverage, so check before relying on a home plan away from your address. See our guide to internet in a caravan, motorhome or boat.
• A short trial of 4G or 5G before committing, on a 30-day plan where one is offered.
• A light user on a tight budget; our guide to free or low-cost ways to get online covers other options.

It's a weaker fit for a busy household relying on it alone, anyone who needs a landline or telecare, and any business use. Browse UK broadband providers or compare broadband deals at your postcode to see what's available where you live.

Don't cancel anything until the new setup has proved itself: test the SIM and router for a few weeks on the shortest term you can, and sort out the phone side (your number, any telecare, 999 in a power cut) first.

When you switch between fixed broadband providers, Ofcom's One Touch Switch process means you contact only the new provider, and your current provider must send you the switching information, including any early-termination charges. A mobile network selling you a SIM isn't taking over your fixed line, so expect to cancel the fixed contract yourself. Ask your current provider for your contract end date, notice period and any early-termination charge in writing first.

Our guide to switching from a fixed line to 4G, 5G or satellite walks through the move. If your home gets good fixed speeds after all, mobile broadband vs home broadband sets out the trade-offs.

• Read the current terms, fair use policy and any traffic-management document for the exact plan, and save a dated copy.
• Ask the network whether its SIM may be used in a third-party router, and keep the reply.
• Find the usage thresholds (such as Vodafone's 200GB flag or the 600GB a month on Vodafone and EE unlimited plans) and estimate your use.
• Check for a tethering device limit: some EE terms documents set one at 12 devices.
• Check coverage for the network the SIM runs on, at the spot where the router will sit.
• Confirm the router is unlocked, supports 4G or 5G and your network's bands, and takes the right SIM.
• Start on a 30-day or one-month plan where one is offered.
• Keep a phone for 999, and plan for telecare and a landline if you need them.
• Compare broadband deals at your postcode before you decide.