I agreed a rent increase by email. Is it valid?
The short answer, for any increase taking effect on or after 1 May 2026, is no. And the consequences are more awkward than most landlords expect, because they cost real money rather than just paperwork.
What changed
There is now one lawful route to a rent increase on an assured tenancy: a section 13 notice on Form 4A, at least two months’ notice, no more than once a year. That is not one option among several. It replaced the alternatives.
So the two things landlords have always done instead both stopped working. A rent review clause in the agreement — the annual CPI or fixed-percentage uplift — can no longer be relied on. And an increase agreed directly with the tenant by letter, text or email is not a valid increase, even where the tenant plainly agreed to it. The tenant's agreement does not make it valid. The law requires the procedure to be followed, whatever the two of you agreed. GOV.UK also confirms that where an increase was agreed before 1 May 2026 but was due to take effect after it, the increase does not apply.
Why this costs money rather than just paperwork
Here is the part that surprises people. If the increase was not validly imposed, the rent under the tenancy never changed. The tenant can lawfully carry on paying the old figure. And the shortfall is not arrears. No higher rent was ever due, so there is no debt. You cannot recover it later, and it is certainly not a basis for a Section 8 notice on rent-arrears grounds. Serving one on the strength of an invalid increase would be a serious own goal.
Which means every month you leave it is a month of the increase you simply do not get. The delay is the cost.
What if the tenant has been paying the higher amount anyway?
Many have, quite happily, because they agreed to it and had no reason to think anything was wrong. That does not retrospectively validate the increase, and a tenant who later takes advice can stop paying the extra and ask for what they overpaid. How likely that is depends on your relationship with the tenant. Either way, serve a valid Form 4A now rather than leaving it running for years.
What to do now
- Work out what the rent actually is under the tenancy — the last figure set by a valid mechanism. That is the real rent, whatever is currently arriving in your account.
- Serve a Form 4A properly. Two months’ notice minimum, starting on a rent day, once a year. Read the three boxes landlords get wrong before you fill it in — you do not want to lose another two months to a defective notice.
- Answer box 4.3 honestly. The informal increase you agreed by email is a rent increase for the purposes of that box, even though it was not validly imposed. If you cannot date it, reconstruct it from your bank statements.
- Tell the tenant plainly what you are doing. A short message — you are formalising the increase you both discussed, using the process the law now requires — keeps a good relationship intact and avoids the notice landing as a shock.
- Decide what to do about the gap. Whether to leave the past overpayment alone or address it is a commercial and relationship judgement, not a legal one. Most landlords say nothing and start clean. Take advice if the sums are significant.
If you are still relying on a rent review clause, read what happened to the terms in your existing agreement — the clause is not the only thing in there that stopped working on 1 May.
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Written statement of terms · Missed the 31 May deadline? · How to increase rent (Form 4A) · Does every tenant need their own copy? · Proving you served it · Why Form 4A notices get rejected · Do you need a deed of guarantee? · Pet rent and pet insurance · The 28-day pet rule