Section 13 rent increases: a diary, the sums and a Form 4A checklist

Who it’s for

Letting agents and property managers in England who review rents for private landlords

Time to set up

1 hour once, then about 20 minutes a notice

Difficulty

Beginner

Monthly cost

£0

You help a letting agent in England prepare a section 13 rent increase for a landlord to approve. Use ONLY the diary row and comparables I paste. Do not invent comparables, dates or rents. Write four parts. (1) CALCULATION NOTE: current rent, proposed rent, the increase in £ a month, the increase as a percentage of the current rent to one decimal place, and the extra rent a year (monthly increase x 12). Show every sum. Then list the agreed-lettings comparables and their average, shown as a sum, and say how far the proposed rent is above or below that average. Keep asking-price adverts in a separate list headed 'weaker evidence'. (2) DATE CHECKS: for each rule, say PASS or FAIL with the dates involved: (a) the new rent date is at least two months after the planned service date; (b) it is at least 52 weeks (364 days) after the last increase took effect, or after the tenancy's first period began if there has been no increase; (c) the 53-week rule: if the date 364 days after the last increase falls more than six days before the anniversary of the first increase after 11 February 2003, the wait is 53 weeks (371 days); (d) the new rent date falls on the first day of a rental period (the rent day); (e) the period is a month or less. Do your own date sums and compare them with the sheet's dates. If yours differ, give both dates and add a short note in brackets saying in plain words what to check, for example (check this date against the tenancy agreement). Never suggest a different date yourself. (3) FORM 4A ANSWERS: list what goes in 4.1 to 4.7, using [NAMES] for the tenants and landlord. Say 'leave blank' where the form says to. (4) COVERING NOTE to the tenant, under 120 words: what is changing, from when, that the official form is enclosed and explains their options, and who to contact. Do not argue the case, do not mention ending the tenancy and do not say the increase is guaranteed. British English. Plain, polite, no legal advice. Diary row and comparables: [paste]

Form 4A, the government’s rent increase notice, contains a sentence most official forms wouldn’t dare: the 53-week rule exists “because 52 weeks is slightly less than a calendar year” (GOV.UK, Form 4A). Raise a rent every 52 weeks on the dot and the date creeps a day or two earlier each year, until the law makes you wait an extra week. That’s the level of date-keeping section 13 now asks of every letting agent in England.

And there’s no other way to do it. Since 1 May 2026, the Act says any term allowing rent to go up other than through section 13 has “no effect” (legislation.gov.uk). The tidy CPI clause in your 2024 tenancy agreements is decoration. GOV.UK’s version: “If you want to increase the rent, you will need to fill out Form 4A and give it to your tenant with at least 2 months’ notice” (GOV.UK). This guide is a diary, a calculation note and a checklist that get the dates right first time. It’s a working method, not legal advice: if a case is unusual, ask a solicitor before you serve.

What does this automation do?

1. A Google Sheet holds every managed tenancy with its rent day, last increase and the first increase after 11 February 2003.
2. Formulas work out the earliest date a new rent can start, the latest day to serve, and your own earlier target.
3. ChatGPT turns one row and your comparables into a calculation note for the landlord, checks the sheet’s dates, lists the Form 4A answers and drafts a covering note.
4. Google Calendar reminds you to talk to the landlord, serve the notice, and watch for a tribunal application.

What do you need before you start?

• Each tenancy agreement, so you know the rent day, the period and any agreed method of serving notices.
• The rent history: when every increase took effect and how (Form 4 notice, tribunal decision or rent review clause).
• A free ChatGPT, Claude or Gemini account, Google Sheets and Calendar, and a downloaded copy of the current Form 4A.

How do I set it up?

Step 1: Know the four rules that decide the date

Form 4A’s own Note A sets these out, and section 13(2), (3A) and (3B) of the Housing Act 1988 are behind them (legislation.gov.uk):

• Two months’ notice. The notice “must be served on the tenant(s) at least two months before the new rent can start” (Form 4A).
• 52 weeks. The first increase can’t start until 52 weeks after the tenancy began. “In most cases, any further rent increase must be at least 52 weeks after the previous increase.” GOV.UK’s tenant guide puts it as “once a year”, and “They cannot increase your rent in the first year of your tenancy” (GOV.UK).
• Sometimes 53 weeks. “The new rent date cannot be more than 6 days before the anniversary of the date given in question 4.4. If it would be, the landlord must wait an extra week (53 weeks in total).” Question 4.4 is the first rent increase after 11 February 2003.
• A rent day. “The new rent must start at the beginning of a tenancy period.” If a monthly tenancy started on the 20th, the new rent starts on the 20th.

Two more from GOV.UK. A rent increase made under a rent review clause before 1 May 2026 still starts the clock: the next section 13 increase can’t take effect until 52 weeks after it (SI 2026/421, reg 7). And Form 4A asks for a rent period of “a month or less”; GOV.UK’s tenant guide says assured periodic tenancies “cannot be for longer than a month at a time”. The form is “For use in the private rented sector in England only”; social landlords use Form 4.

Step 2: Build the rent review diary

One row per tenancy, with these columns:

Column H matters more than it looks. GOV.UK’s tribunal guidance says a notice must “not increase the rent within 52 weeks of the last increase, or during a fixed-term tenancy” (GOV.UK), so you need the true last date, not the date the landlord remembers.

Step 3: Let the sheet work out the dates

Put these in row 2 and fill down. Dates must be real dates in the sheet, not text.

• J, 52 weeks: =IF(G2="", D2+364, G2+364)
• K, 53-week flag: =IF(OR(G2="", I2=""), "n/a", IF(J2 < EDATE(I2, 12*ROUND((J2-I2)/365.25, 0)) - 6, "53 WEEKS: check", "52 weeks ok"))
• L, earliest allowed: =IF(K2="53 WEEKS: check", G2+371, J2)
• M, proposed new rent date (the next rent day on or after L): =IF(DATE(YEAR(L2), MONTH(L2), E2) >= L2, DATE(YEAR(L2), MONTH(L2), E2), EDATE(DATE(YEAR(L2), MONTH(L2), E2), 1))
• N, serve-by: =EDATE(M2, -2)
• O, our target service date: =WORKDAY(N2, -10), two working weeks of slack
• P, landlord chat: =WORKDAY(O2, -5)

Then add three Calendar events per tenancy: P (agree the rent), O (serve) and the day before M (last day for a tribunal application). Column M is the earliest date, not a target: a later rent day is always allowed.

The formulas are ours, so treat them as a calculator you check. One known weak spot: rent days of the 29th, 30th or 31st (February will fight you, so check M by hand). Column K compares J with the anniversary of column I nearest to it, so it copes with New Year. We checked it in Python against our reading of section 13(3B) across 200,000 random date pairs. It only disagreed where the last increase fell about six months off the usual cycle, and there the law’s “anniversary” is unclear anyway, so work those out by hand against Form 4A Note A3. Not verified: GOV.UK doesn’t say whether “two months” can be cut to the exact day, which is why column O builds in ten working days.

Step 4: Gather comparables the tribunal would rate

If the tenant challenges, the tribunal decides “what rent the landlord could reasonably expect if the property were let on the open market on the same terms” (Form 4A). GOV.UK tells tenants that information from Rightmove and Zoopla “can help but evidence from actual agreed lettings (rental agreements) is stronger” (GOV.UK). You have something tenants mostly don’t: your own let-agreed records.

So pick three to five agreed lettings of similar size, features and location from the last six months, with the date each was let. Keep asking prices in a separate, weaker list. The tribunal “can consider other factors like the condition of the property”, so note anything that drags this one below its neighbours, like the kitchen nobody’s touched since 2009.

Step 5: Write the calculation note with ChatGPT

Paste one diary row and the comparables into the prompt below. Use the property and a reference, not the tenants’ names: the names go on the form, by hand. ChatGPT shows the increase in £ and as a percentage, the extra a year, the comparables average, and a pass or fail for every date rule.

The point of making it redo the dates is a second opinion on the formulas, not a replacement for them. If it flags a date to check, one of you is wrong, and it’s your job to find out which with a calendar. It never picks a date.

The note is what you send the landlord: “£60 a month more, 5.2%, £720 a year, £10 below three agreed lettings” is a conversation a landlord can say yes to in one email. If the tenant pushes back, section 13 lets you both agree a lower figure than the notice, not a higher one (legislation.gov.uk).

Step 6: Fill in Form 4A and run the checklist

Download the current form from GOV.UK’s assured tenancy forms page each time, because the date code at the bottom (05.26 today) can change. GOV.UK is blunt: “Do not change the wording of these forms unless the form says you can. If you change the wording, the form may not be valid.” So fill in the answers; don’t paste ChatGPT’s text over the notes.

Before anyone signs:

• Current Form 4A downloaded today, from GOV.UK
• 1.1: every joint tenant named
• 2.3 and 3.3: if you give an email address, you agree the tenant and the tribunal “may use this address to serve documents on you”
• 4.1 and 4.5: frequency is the tenancy period, a month or less
• 4.3: most recent increase, or blank if none
• 4.4: first increase after 11 February 2003, or blank if none
• 4.6: matches diary column M, falls on a rent day, and passes all four rules
• 4.7: only charges included in the rent; “nil” where none; no variable service charges
• Signed by the landlord or the landlord’s agent, with print name and date; joint landlords sign or agree one signs for all
• The landlord has approved the figure in writing

Step 7: Serve it, keep the proof and diary the tribunal window

Form 4A’s note to landlords: “You need to be able to evidence that you served the notice on your tenant.” If the written agreement sets out how notices are served, use that. If not, the form lists three ways: “handing it over to your tenant in person, leaving it at the tenant’s address or sending it by registered post.” Email only works if the agreement allows it, as GOV.UK’s tenant guide says (GOV.UK).

Record the date, time, method and who served it in column Q, with a photo of the envelope through the door or the registered post receipt. Not verified: neither the form nor the GOV.UK pages we read say when a posted notice counts as served, so post early or deliver by hand.

Then the tribunal window. A tenant who disagrees must get their application to the tribunal before the date in 4.6 (it costs them £47). If they apply, the landlord can reply on form MR2 within 28 days, and the tenant can answer on MR3 (GOV.UK). If the tribunal decides the notice is invalid, “it will not determine the rent and you do not need to pay the new proposed rent”. That’s why Steps 3 and 6 exist. On the morning of the start date, check for tribunal post, remind the tenant to update their standing order (Form 4A tells them to), and set column R.

The copy-paste prompt

You help a letting agent in England prepare a section 13 rent increase for a
landlord to approve. Use ONLY the diary row and comparables I paste. Do not
invent comparables, dates or rents. Write four parts. (1) CALCULATION NOTE:
current rent, proposed rent, the increase in £ a month, the increase as a
percentage of the current rent to one decimal place, and the extra rent a year
(monthly increase x 12). Show every sum. Then list the agreed-lettings
comparables and their average, shown as a sum, and say how far the proposed
rent is above or below that average. Keep asking-price adverts in a separate
list headed 'weaker evidence'. (2) DATE CHECKS: for each rule, say PASS or
FAIL with the dates involved: (a) the new rent date is at least two months
after the planned service date; (b) it is at least 52 weeks (364 days) after
the last increase took effect, or after the tenancy's first period began if
there has been no increase; (c) the 53-week rule: if the date 364 days after
the last increase falls more than six days before the anniversary of the first
increase after 11 February 2003, the wait is 53 weeks (371 days); (d) the new
rent date falls on the first day of a rental period (the rent day); (e) the
period is a month or less. Do your own date sums and compare them with the
sheet's dates. If yours differ, give both dates and add a short note in
brackets saying in plain words what to check, for example (check this date
against the tenancy agreement). Never suggest a different date yourself. (3)
FORM 4A ANSWERS: list what goes in 4.1 to 4.7, using [NAMES] for the tenants
and landlord. Say 'leave blank' where the form says to. (4) COVERING NOTE to
the tenant, under 120 words: what is changing, from when, that the official
form is enclosed and explains their options, and who to contact. Do not argue
the case, do not mention ending the tenancy and do not say the increase is
guaranteed. British English. Plain, polite, no legal advice. Diary row and
comparables: [paste]

What can go wrong?

• Trusting the CPI clause. It has “no effect” now. Only Form 4A puts the rent up.
• Counting a year, not 52 weeks. GOV.UK’s tenant guide says “once a year”, but the date the law tests is 52 weeks, or 53 if the date has drifted. Column K is there for that.
• A start date that isn’t a rent day. A notice for the 1st on a tenancy that pays on the 14th fails Note A4, however good the rent is.
• The tenant’s options. The tenant “will not be required to pay more than the rent the landlord first proposed”, and doesn’t pay the new rent until the tribunal decides. So an optimistic figure can cost the landlord months of the old rent.
• Rewording the form. Fill in the boxes. GOV.UK says changed wording “may not be valid”.
• Wales and Scotland. Form 4A is England only. Properties elsewhere have their own rules.

Once the rents are sorted, the landlord register tracker keeps the certificates in the same kind of sheet, and the repair message triage handles the tenant who replies to the rent notice about the boiler. One practical automation like this, with the £ and the hours it saves, lands in your inbox every Friday if you join our free email.

Frequently asked questions

Sources

1. GOV.UK: Renters' Rights Act, an overview for landlords (1 May 2026)
2. GOV.UK: Assured tenancy forms (Form 4A, 1 May 2026)
3. GOV.UK: Form 4A, landlord's notice proposing a new rent (05.26)
4. GOV.UK: Apply for an open market rent determination (10 August 2026)
5. GOV.UK: Assured periodic tenancies, a guide for tenants
6. GOV.UK: Assured periodic tenancies, a guide for tenants: Rent increases
7. legislation.gov.uk: Housing Act 1988, section 13
8. legislation.gov.uk: Renters' Rights Act 2025, section 6
9. legislation.gov.uk: Renters' Rights Act 2025 (Commencement No. 2 and Transitional and Saving Provisions) Regulations 2026 (SI 2026/421)

This guide is general information, not legal, tax or financial advice. Tool prices and screens change; we re-check every guide regularly. Spotted something out of date? Tell us and we’ll fix it.