If you’re thinking about co-signing a lease for someone in the UK, you need to understand that you’re taking on a legal obligation that can last for years and cost you thousands of pounds. I’ve covered tenancy law for long enough to see the same pattern repeat: a friend or family member asks for help, the co-signer signs without reading the fine print, and then the tenant moves out early or stops paying rent. The landlord comes straight to the guarantor. It’s a position that leaves many people blindsided, and the rules are about to change in a major way.
From May 2026, the Renters’ Rights Act will abolish Section 21 “no-fault” evictions and replace fixed-term assured shorthold tenancies with a single system of periodic tenancies. That shift changes what a co-signer is actually on the hook for. If you’re considering co-signing — or you’ve already done it — you need to know how these reforms affect your liability. Here’s what you actually need to know.
What a Lease Co-Signer Actually Agrees To
The most important thing to understand is that co-signing isn’t a moral gesture — it’s a financial guarantee. When you sign as a guarantor or co-signer, you’re telling the landlord: if the tenant doesn’t pay, I will. That’s the core of it. Under the current system, most tenancies run as assured shorthold tenancies (ASTs) with a fixed term, often six or twelve months. But from May 2026, new tenancies in England will become assured periodic tenancies with no fixed end date. That means your liability as a co-signer doesn’t automatically stop when the original term would have ended.
I’d never sign a guarantee without first asking the landlord or letting agent for a written breakdown of exactly what I’m liable for. If they can’t or won’t provide it, that’s a red flag. You can also spot the red flags in a rental agreement before you commit — things like vague clauses about “all costs” or “any losses” can come back to bite you.
Why the Renters’ Rights Act Changes Everything for Co-Signers
The Renters’ Rights Act 2025 received Royal Assent in late 2025 and its first major phase kicks in from May 2026. For co-signers, the biggest shift is the move away from fixed-term tenancies. Under the old system, a six-month AST gave you a clear end date. If the tenant stayed on after that, they’d be on a periodic tenancy — but many guarantor agreements specifically covered only the fixed term. The new system removes that clarity.
Here’s a scenario that comes up more often than you’d think. Say you co-signed for a one-year AST starting in March 2026. In May 2026, the new rules take effect. The tenancy converts to an assured periodic tenancy. Your co-signer agreement, if it’s broadly worded, may still apply. The tenant loses their job six months later. The landlord comes to you for the unpaid rent. You thought you were off the hook after twelve months. You’re not.
What I notice is that most people assume a co-signer’s responsibility ends when the fixed term ends. That assumption is dangerous now and will be even more so after May 2026. If you’re already a co-signer, check your agreement for a clause that says your liability continues until the tenancy ends — not just the fixed term. If you’re thinking about co-signing, ask for a guarantee that explicitly limits your liability to a specific period or a capped amount. A clear understanding of tenant rights helps you know what the landlord can and cannot demand from you.
Where Co-Signers Get Tripped Up
The mistakes I see fall into a few predictable categories. Each one is avoidable if you know what to look for.
Signing Without a Cap on Liability
Many guarantor agreements don’t put a pound sign on your exposure. You could be liable for rent arrears, damage, legal fees, and even the cost of re-letting the property. A landlord who fails to provide the required Information Sheet by the deadline faces a fine, but that doesn’t reduce what you owe. I’d insist on a written cap — say, six months’ rent or a fixed amount — before signing anything.
Assuming the Tenant’s Deposit Covers Everything
The tenancy deposit is usually capped at five or six weeks’ rent. If the tenant causes £3,000 in damage and the deposit is only £1,200, the landlord can come after you for the difference. The deposit is a buffer, not a shield. Make sure you see the inventory check-in and check-out reports so you know what condition the property was in at the start.
Ignoring the Rent Increase Clause
Under the Renters’ Rights Act, landlords can increase rent only once per year through a prescribed process. But if your guarantor agreement says you’re liable for “all rent due under the tenancy,” that includes any lawful increase. You could end up paying more than you budgeted for. Ask the landlord to confirm in writing that your liability is capped at the initial rent amount.
Not Understanding the New Periodic Tenancy Rules
From May 2026, most tenancies will be periodic from the start. That means there’s no fixed end date. Your liability as a co-signer could stretch on indefinitely unless the agreement says otherwise. If you’re co-signing after that date, make sure the guarantee has a clear end date or a specific trigger that ends your obligation — like the tenant finding a replacement guarantor.
→ Scroll right to see all columns
| Tenancy Type | Before May 2026 | From May 2026 |
|---|---|---|
| Fixed term | Standard AST with set end date | No new ASTs; periodic from start |
| Co-signer liability | Often limited to fixed term | Continues until tenancy ends |
| Eviction route | Section 21 (no-fault) available | Section 21 abolished; must use Section 8 grounds |
How to Protect Yourself as a Co-Signer
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If you’re going to co-sign, you need a plan. Here’s what I’d do in your position.
Get the Guarantee in Writing and Keep a Copy
Verbal agreements are nearly impossible to enforce, but a written guarantee is binding. Make sure the document clearly states your name, the tenant’s name, the property address, the rent amount, and the duration of your liability. Keep a digital and physical copy. If the landlord tries to claim you agreed to something you didn’t, you have proof.
Limit Your Liability to a Specific Amount or Period
Ask for a clause that says your total liability is capped at, for example, six months’ rent. Some landlords will agree to this because they’d rather have a co-signer with a cap than no co-signer at all. If they refuse, consider whether the risk is worth it. You can also ask for a “replacement guarantor” clause that lets you step away once the tenant finds someone else to take your place.
Check the Tenant’s Rental History and Affordability
Before you sign, ask the tenant for proof of income and a credit report. If they’ve missed payments before, that’s a warning sign. You can also ask the landlord to confirm that the tenant’s rent is no more than 30-35% of their take-home pay. If it’s higher, the risk of default goes up. A rookie mistake many tenants make is overstretching their budget — and as a co-signer, you pay the price.
Know Your Rights Under the New Rules
From May 2026, landlords must follow a stricter process to evict tenants. That means they can’t simply kick someone out and then come after you for the remaining rent. If the landlord fails to provide the Information Sheet by 31 May 2026, they face a fine of up to £7,000. That doesn’t cancel your debt, but it does give you leverage if the landlord tries to cut corners. If you’re unsure about your position, it’s worth speaking to a tenant landlord lawyer who can review the agreement before you sign.
Frequently Asked Questions
Can I be held liable for rent after the fixed term ends? ▾
What happens if the tenant damages the property? ▾
Can I remove myself as a co-signer? ▾
Does the Renters’ Rights Act affect existing guarantor agreements? ▾
What if the landlord doesn’t give the tenant the Information Sheet? ▾
The bottom line is this: co-signing a lease is a serious financial commitment that can last longer than you expect, especially with the new tenancy rules coming in May 2026. Before you sign, get the agreement in writing, cap your liability, and check the tenant’s ability to pay. If this was useful, you might also want to read UK Landlords’ Top Apartment Lease Mistakes.
Sources and Further Reading
Renting with Pets in the UK: Is It Really That Hard? — A practical look at how pet clauses affect tenancy agreements and what co-signers should watch for.
Renters’ Rights Act Information Sheet. UK Government, 2026.
Key Legislative and Legal Updates for 2026. James & Sons, 2026.
UK Property Management Legislation Updates: Key Changes for Q1/Q2 2026. POD Management, 2026.
