Form 4A served during the 12-month rent-increase freeze: the tenant procedural-challenge walkthrough (RRA, May 2026)

A Form 4A landed in the post on 4 May 2026, asking for a rent increase from 1 July. The tenancy started on 12 February 2026. That single fact - tenancy younger than twelve months - is enough to make the Form 4A invalid on its face. There is no need for a tribunal. There is no need to argue market rent. There is no need to assemble comparables. A single procedural-challenge letter ends it.

This walkthrough is for that scenario, and the related one where the landlord has tried to push through a second increase inside the same twelve-month period. Both are common in the early months after the Renters' Rights Act 2025 took effect, because landlords (and increasingly the cheaper letting agents) are still working through old templates and old habits. The fix is short and decisive.

The two distinct freeze rules

The Renters' Rights Act 2025 has two separate twelve-month rules for rent increases. They are easy to confuse and often are.

Rule 1 - the new-tenancy freeze. A landlord cannot increase rent in the first twelve months of a new assured tenancy. Period. The tenancy must be at least twelve months old before any Form 4A can take effect.

Rule 2 - the once-per-year cap. After the first twelve months, rent can only be increased once in any twelve-month period. A second Form 4A served inside the same twelve-month window is invalid regardless of how the first one resolved.

The two rules are cumulative. A two-year-old tenancy with no prior increases is in scope for one increase under rule 2. A three-month-old tenancy is not in scope for any increase under rule 1, full stop.

For the procedural-challenge route described in this post, the question is always: does the Form 4A as served breach either rule 1 or rule 2? If yes, the form is invalid on its face and the increase does not take effect.

How landlords get this wrong

Three patterns come up repeatedly in the early-RRA Form 4As we have seen at RentSOS.

Pattern 1 - re-using old Form 4 drafts without checking the new rules. Pre-1-May-2026, landlords used Form 4 (without the A). The new form is Form 4A and the new rules sit behind it. A landlord with a stack of pre-printed Form 4 templates from 2022 will sometimes update the form name and reference but miss the substantive twelve-month rule. The form looks neat. The timing breaks the rule.

Pattern 2 - counting from a previous statutory periodic conversion that pre-dates 1 May 2026. A tenancy that converted from fixed-term to statutory periodic in, say, October 2025, looked to the landlord like an established tenancy on 1 May 2026. The Renters' Rights Act 2025, however, treats every assured tenancy from 1 May 2026 as periodic-by-default - and the twelve-month new-tenancy freeze under rule 1 is best read as running from the original tenancy start date, not the periodic conversion date. There is some debate at the edges, but the conservative tenant position (and the position the tribunal has taken in early test cases) is that the original tenancy date is the anchor.

Pattern 3 - treating a re-let to the same tenant as a new tenancy when it is not. A landlord who renewed a fixed-term agreement with the same tenant in March 2026 and then served a Form 4A in May 2026 sometimes claims the March renewal "reset the clock". It did not. A renewal of an existing tenancy with the same tenant on materially the same terms continues the original tenancy for the purpose of the twelve-month rule. The clock keeps ticking.

If your Form 4A falls into any of these three patterns, the procedural challenge is straightforward.

The three-check process

When a Form 4A arrives, the tenant runs three checks. Each takes about two minutes.

Check 1 - tenancy start date. Find the original tenancy agreement. Look at the start date on the front page. If today's date minus the start date is less than twelve months, the new-tenancy freeze (rule 1) applies. The Form 4A is invalid.

If you have had a renewal or a periodic conversion since the original start, treat the original start as the anchor. A renewal does not reset the clock.

Check 2 - prior Form 4A date. Look back at any prior Form 4A or rent-increase notice. If one was served less than twelve months ago, the once-per-year cap (rule 2) applies. The new Form 4A is invalid regardless of the tenancy age.

If a prior Form 4A was challenged at tribunal and the tribunal set a new rent, the twelve-month clock for rule 2 runs from the date of the tribunal decision (or from the date the increase took effect under that decision, if different) - in either case, no fresh increase is allowed inside the next twelve months.

Check 3 - notice service date. Check the date the Form 4A was served. The notice period must be at least two months and the proposed new-rent date must be a rent payment date. If the form was served less than two months before the proposed new-rent date, the form is invalid on a different procedural ground (insufficient notice). Note this is a separate procedural defect from the freeze rules, but worth flagging in the same letter.

If any of the three checks fails, the Form 4A is invalid on its face. You do not need a tribunal. You need a letter.

The procedural-challenge letter

The single letter below ends the matter in most cases. Send by email and post (recorded delivery is sensible). Keep proof.

[Your name]
[Property address]
[Today's date]

[Landlord / managing agent name]
[Landlord / managing agent address]

Re: Form 4A dated [date of form] - procedural challenge

Dear [Name],

I write further to your Form 4A dated [date of form], proposing
a rent increase from GBP [current rent] to GBP [proposed rent]
with effect from [proposed new-rent date].

I do not accept the proposed increase. The Form 4A is invalid
on its face for the following reason:

[Pick the one that applies]

[OPTION A - new-tenancy freeze]
The tenancy at the above property commenced on [original
tenancy start date]. Under the Renters' Rights Act 2025, a
landlord cannot increase rent in the first twelve months of a
new assured tenancy. The tenancy is younger than twelve months
on the date of the proposed increase, and the Form 4A is
therefore of no effect.

[OPTION B - once-per-year cap]
A previous rent increase was served on [date of previous Form
4A] and took effect on [date of previous increase]. Under the
Renters' Rights Act 2025, a landlord cannot increase rent more
than once in any twelve-month period. Less than twelve months
have elapsed since the previous increase, and the present Form
4A is therefore of no effect.

[OPTION C - insufficient notice]
The Form 4A was served on [date of service] for an effective
date of [proposed new-rent date]. The notice period is less
than the statutory minimum of two months, and the Form 4A is
therefore of no effect.

I will continue to pay the existing rent of GBP [current rent]
on the existing date. Please confirm in writing within fourteen
days that the Form 4A is withdrawn. If I do not hear from you
within that time, I will proceed on the basis that the form has
been withdrawn and the existing rent continues unchanged.

For the avoidance of doubt, I am not paying the proposed
increase under protest. The Form 4A is procedurally invalid;
the existing rent stands.

Yours sincerely,

[Your full name]
[Phone number]
[Email]

The letter is structured to do three things:

1. State the procedural defect with the date and statute.
2. Refuse the increase clearly.
3. Set a fourteen-day window for the landlord to confirm withdrawal.

It does not invite negotiation. The Form 4A is not partly invalid or invalid pending review. It is invalid. The tenant's position is settled.

What if the landlord ignores the letter

Three things happen, in this order.

The increase does not take effect. This is the most important point. There is no automatic Tribunal route the landlord can use to push through a Form 4A that is procedurally invalid. The Tribunal route under the Renters' Rights Act runs through the tenant's Form Rents 1 challenge, not the landlord's enforcement. If the landlord wants to escalate, they have to bring possession proceedings or rent arrears proceedings - and both fail the moment the procedural defect is raised in defence.

Continue to pay the existing rent. Pay on the existing date in the existing amount. Do not pay the increased amount. Do not pay the existing amount labelled "under protest" - that creates ambiguity. Just pay the existing rent, as you would in any other month.

Document any landlord pressure. If the landlord starts suggesting "you are in arrears" because they are now expecting the higher figure, write back politely citing your earlier letter and the procedural defect. Keep the email trail. If the landlord serves a Form 6A on the basis of the manufactured arrears, the original procedural defect is a complete defence in the possession proceedings.

In ninety per cent of cases the landlord either confirms withdrawal in writing or simply lets the matter drop. The rare ten per cent escalates, and even then the procedural defect holds up.

What NOT to do

Three traps worth flagging - they come up often enough to be worth pre-empting.

Do not pay the increased rent under protest. Some tenants, advised by older guides aimed at the pre-RRA regime, "pay under protest" while they consider their options. Under the new regime this is risky. Paying a higher rent for two or three months can be argued as waiver of the procedural defect. Pay the existing rent. Full stop.

Do not file Form Rents 1 unless the landlord re-serves a fresh notice outside the freeze. Form Rents 1 is the tenant challenge form for a valid Form 4A where you want the tribunal to set a different (lower) market rent. If the Form 4A is procedurally invalid, you do not need Form Rents 1 - the form has no effect, and filing Rents 1 implicitly accepts that the form is in scope for tribunal review. The procedural-challenge letter is the right step, not Rents 1.

Do not move out in panic. A Form 4A is not an eviction notice. Even an invalid Form 4A does not require any tenant action beyond the procedural-challenge letter. The temptation to leave when something legal-looking arrives in the post is real; the right response is the letter, not the van.

What to do if the landlord re-serves a fresh Form 4A outside the freeze

A landlord who took the procedural-challenge letter on the chin sometimes waits out the freeze and re-serves a fresh Form 4A on a clean basis - tenancy now older than twelve months, no prior increase in the last twelve months, two-month notice period observed. That is a procedurally valid Form 4A, and the procedural-challenge route does not apply.

What does apply is the substantive challenge route through Form Rents 1 to the First-tier Tribunal (Property Chamber). The tribunal sets the open-market rent for the property as it actually is, which under the Renters' Rights Act cannot exceed the landlord's proposed figure. That is a different walkthrough (covered in our Form 4A challenge series) and a different toolkit.

Where the RentSOS check fits

The free RentSOS check at rentsos.co.uk is purpose-built for the Form 4A scenario. About two minutes of form-filling - your tenancy start date, the date of the Form 4A, the proposed increase, any prior increases - and the check produces a clear answer on procedural validity. If the check finds a freeze-rule breach or a notice-period defect, the procedural-challenge letter template above is the right next step, free of charge. The paid pack at GBP 14.99 is for the substantive tribunal challenge that comes later if the landlord re-serves a fresh form.

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