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Rent Increases (Form 4A)

Form 4A Box 4.6 Start Date Calculation: How to Avoid Section 13 Tribunal Rejection in England

Step-by-step statutory guide to calculating Box 4.6 on GOV.UK Form 4A in England under Housing Act 1988 s.13(2)–(3B) and SI 2026/354: deemed service, 2-month notice, 52/53-week floors, and rent period alignment.

Last reviewed: 27 October 2026 · About 10 min read · England only

Why Box 4.6 is the #1 cause of invalid Section 13 notices

From 1 May 2026, section 13 of the Housing Act 1988 (as amended by section 6 of the Renters' Rights Act 2025) is the sole lawful mechanism for increasing the rent under an assured periodic tenancy in England. Contractual rent review clauses are rendered void by section 13(4A), and the old pre-May 2026 Form 4 is replaced by Form 4A (Landlord's notice proposing a new rent under an assured periodic tenancy of premises situated in England, version 05.26), prescribed by Regulation 3(1)(d) of the Assured Tenancies (Private Rented Sector) (Prescribed Forms and Transitional Provisions) (England) Regulations 2026 (SI 2026/354) and published at GOV.UK's assured tenancy forms guidance (Form 4A).

On page 3 of Form 4A, Box 4.6 asks for a single 8-digit date (DD MM YYYY):

"The proposed new rent will take effect on: [Day] [Month] [Year]"

At the First-tier Tribunal (Property Chamber), Box 4.6 is strictly construed. If the date you write in Box 4.6 falls even one day earlier than the earliest date permitted by statute—or if it lands on a calendar day that is not the first day of a period of the tenancy—the notice is invalid. The Tribunal cannot amend an invalid Box 4.6 date for you; you must serve a fresh Form 4A and wait another two full calendar months.

Instant Calculation: Want to check your exact Box 4.6 date right now? Open our free Section 13 (Form 4A) Earliest Start Date Calculator, which runs all four statutory rules below and lets you pre-fill your official Form 4A in one click.

The 4 statutory rules every Box 4.6 date must satisfy simultaneously

Under section 13(2), (3A), and (3B) of the Housing Act 1988 and the Notes to Form 4A (SI 2026/354), the date entered in Box 4.6 must satisfy all four of the following conditions at the same time:

RuleStatutory AuthorityLegal RequirementMathematical Formula (@signwise/calc)
Rule 1: Minimum 2 Calendar Months' NoticeHousing Act 1988 s.13(2)(a) & Form 4A Note A11The Box 4.6 start date must be at least two calendar months after the date on which the notice is served on the tenant.min_after_service = addDays(addCalendarMonths(service_date, 2), 1) (clamping end-of-month dates to the last day of the target month, plus a 1-day clear buffer).
Rule 2: 52-Week Initial Tenancy FloorHousing Act 1988 s.13(2)(b) & Form 4A Box 4.2 / Note A12If this is the first rent increase since the tenancy began, the Box 4.6 start date cannot be earlier than 52 weeks (364 days) after the date the tenancy started.min_after_start = addDays(tenancy_start_date, 364).
Rule 3: 52/53-Week Previous Increase FloorHousing Act 1988 s.13(3A)–(3B), SI 2026/421 reg 7(2) & Form 4A Boxes 4.3–4.4If the rent has previously been increased (by Section 13 notice, Tribunal determination, or a pre-1 May 2026 rent review clause), Box 4.6 cannot be earlier than 52 weeks (364 days)—or 53 weeks (371 days) where s.13(3B) applies—after the date the last increase took effect.appropriate_date = addDays(last_increase_date, 364) (or + 371 days where s.13(3B) anniversary drift > 6 days applies).
Rule 4: First Day of a Period of the TenancyHousing Act 1988 s.13(2) & Form 4A Note A4The proposed new rent must begin on the first day of a period of the tenancy (for example, the 1st of the month if rent periods run from the 1st to the last day of each month).Let floor = max(min_after_service, min_after_start, appropriate_date, rrc_floor). Advance d from floor to the smallest date where isRentPeriodStart(d, anchor, frequency) === true.

Because Rule 4 snaps the date forward to the next rent period start on or after the combined statutory floor (max(Rule 1, Rule 2, Rule 3)), missing a rent period boundary by 24 hours pushes your earliest lawful rent increase back by an entire rental month.

The postal & email service trap: why dispatch date is not service date

The most common mistake landlords make when completing Box 4.6 is counting two calendar months from the date they sign or post the form, rather than the date the form is served (received or deemed received by the tenant).

As page 1 of Form 4A warns landlords:

"The minimum period that must pass between the date the notice is served and the date the proposed new rent takes effect is two months... If you send the notice by post, you must allow enough time for it to be delivered."

To prevent a Section 13 notice from being struck out at the First-tier Tribunal over a 24-hour delivery dispute, SignWise's calculation engine (@signwise/calc) applies the following deemed-service rules before starting the 2-month clock:

  1. Personal handover to the tenant (+0 days): Service occurs on the day you hand the signed Form 4A to the tenant in person (RI-Q052).
  2. Leaving at the property / through the letterbox (+0 days): Service occurs on the day you deliver the envelope through the property's letterbox (provided your tenancy agreement permits service by leaving notices at the property, or personal delivery is evidenced with a time-stamped photograph and witness signature on your Certificate of Service).
  3. Email (+1 working day conservative buffer): First check that your written tenancy agreement expressly permits service of statutory notices by email and lists the tenant's current email address. Even where permitted, tenancy service clauses often deem an email sent after 4:30 pm or on a weekend to be served on the next working day. Adding a 1-working-day buffer (addWorkingDays(RI-Q052, 1)) prevents an evening email from invalidating Box 4.6.
  4. Registered / First-Class Post (+2 working days conservative buffer): Under section 7 of the Interpretation Act 1978 and Civil Procedure Rule 6.26, postal service is deemed to occur in the ordinary course of post (typically the second business day after posting, skipping weekends and bank holidays). SignWise adds 2 working days (addWorkingDays(RI-Q052, 2)) before calculating the 2-month notice period.

3 worked examples (hand delivery, registered post, and end-of-month clamping)

Worked Example 1: Why Registered Post on the 30th costs you a full month's rent increase

  • Tenancy start date (Box 4.2): 1 June 2025 (52-week floor under s.13(2)(b) was 31 May 2026 — already passed).
  • Rent frequency & period anchor: £1,400 per month, rent period starts on the 1st of each month.
  • Previous rent increases: None.
  • Scenario A — Hand delivery on Friday 30 October 2026:
  • Deemed service date: 30 October 2026.
  • 2 calendar months + 1 day buffer (Rule 1): 31 December 2026.
  • Next rent period start on or after 31 December 2026 (Rule 4): 1 January 2027 (01 01 2027).
  • Scenario B — Sent by Registered Post on Friday 30 October 2026:
  • Planned dispatch date: 30 October 2026.
  • Deemed service date (+2 working days, skipping Saturday 31 Oct & Sunday 1 Nov): Tuesday 3 November 2026.
  • 2 calendar months + 1 day buffer (Rule 1): 4 January 2027.
  • Next rent period start on or after 4 January 2027 (Rule 4): 1 February 2027 (01 02 2027).
  • Takeaway: Posting on Friday 30 October instead of delivering by hand pushes deemed service into November, meaning a Box 4.6 date of 1 January 2027 would be invalid and your earliest valid date moves to 1 February 2027.

Worked Example 2: The 52-week anniversary floor overrides the 2-month notice period

  • Tenancy start date (Box 4.2): 15 May 2026 (monthly rent due on the 15th of each month).
  • Planned hand-delivery date: 10 January 2027.
  • Calculation:
  • Rule 1 (2 months + 1 day after 10 Jan 2027): 11 March 2027.
  • Rule 2 (52 weeks = 364 days after 15 May 2026 under s.13(2)(b)): 14 May 2027.
  • Combined floor (max(11 March 2027, 14 May 2027)): 14 May 2027.
  • Rule 4 (Next rent period start on the 15th on or after 14 May 2027): 15 May 2027 (15 05 2027).
  • Takeaway: Even though you served Form 4A in January 2027 (more than 4 months in advance), Box 4.6 cannot be earlier than 15 May 2027 because s.13(2)(b) prohibits any increase from taking effect within the first 52 weeks of the tenancy.

Worked Example 3: End-of-month rent periods (29th, 30th, or 31st of the month)

  • Tenancy start date (Box 4.2): 31 August 2025 (monthly rent period anchored to the 31st / last day of each month).
  • Planned hand-delivery date: 15 December 2026.
  • Calculation:
  • Rule 1 (2 months + 1 day after 15 Dec 2026): 16 February 2027.
  • Rule 4 (Next monthly period start anchored to day 31 in February 2027, which has 28 days): Under @signwise/calc's isRentPeriodStart clamping rule (Math.min(anchor.getUTCDate(), daysInMonthUtc(2027, 2))), the February period start falls on 28 February 2027 (28 02 2027).

Edge cases: the s.13(3B) 53-week drift rule and pre-May 2026 rent review clauses

Two statutory edge cases frequently catch out landlords who calculate Box 4.6 on a spreadsheet:

  1. Why Box 4.4 exists — The 53-week drift rule (Housing Act 1988 s.13(3B)):

Why does statute say 52 weeks (364 days) rather than "12 calendar months"? Because 52 weeks is 364 days—one day shorter than a standard 365-day calendar year (and two days shorter than a leap year). If a weekly or 4-weekly tenancy increased its rent every 364 days year after year, the annual increase date would drift backward by 1–2 days each year. Under section 13(3B), if subtracting 364 days from the annual anniversary of the first rent increase after 11 February 2003 (Box 4.4) leaves a gap of more than 6 days, the minimum interval for that year becomes 53 weeks (371 days) instead of 52 weeks.

  1. Pre-1 May 2026 Rent Review Clauses (SI 2026/421 Regulation 7(2)):

Suppose your pre-1 May 2026 written AST contained an annual rent review clause, and you last increased the rent under that clause on 1 March 2026 (before the Renters' Rights Act 2025 commenced on 1 May 2026). Even though that March 2026 increase was not made using a Section 13 notice, Regulation 7(2) of SI 2026/421 provides that your first post-commencement Form 4A increase cannot take effect earlier than 52 weeks (364 days) after that last rent review clause increase (i.e. on or after 28 February 2027, snapped to the next rent period start on 1 March 2027).

Eliminate Box 4.6 Calculation Errors: Check your dates for free with the Section 13 Date Calculator, or Generate your Official Form 4A + Certificate of Service & Section 14 Tribunal Evidence Pack (£12).

Frequently asked questions

Can I still use old Form 4 for a Section 13 rent increase in England?
No. From 1 May 2026, old Form 4 is obsolete for private assured periodic tenancies in England. You must use Form 4A (version 05.26), prescribed by Regulation 3(1)(d) of the Assured Tenancies (Private Rented Sector) (Prescribed Forms and Transitional Provisions) (England) Regulations 2026 (SI 2026/354), available via GOV.UK's assured tenancy forms page.
What happens if my Box 4.6 date is one day short of two calendar months?
Under section 13(2)(a) of the Housing Act 1988, a Form 4A notice that gives less than two months' notice from the date of service—or specifies a start date that is not the first day of a period of the tenancy—is invalid. If challenged at the First-tier Tribunal (Property Chamber), the notice will be set aside and you will have to serve a new Form 4A with a fresh two-month notice period.
Does SignWise re-typeset Form 4A or use the official GOV.UK PDF?
SignWise populates the official, unaltered GOV.UK Form 4A AcroForm PDF (SI 2026/354) directly from your validated answers, and appends a separate 3-part annex containing your Statutory Validity Audit, Certificate of Service, and First-tier Tribunal (Section 14) Comparable Market Rent Worksheet.

SignWise is a self-serve document preparation service operated by Ditra (established in Spain). SignWise is not a law firm, is not regulated by the Solicitors Regulation Authority (SRA), does not provide legal advice, and does not carry on reserved legal activities under the Legal Services Act 2007 (section 12 and Schedule 2, paragraph 5). You prepare your document from your answers, review it carefully, and sign it yourself. SignWise is not responsible for legal outcomes. Seek independent legal advice if you are unsure whether a document suits your property or circumstances.

This guide is general information for landlords in England. It is not legal advice. Laws and official forms change; check the linked GOV.UK and legislation pages for the latest position.

Form 4A Box 4.6 Start Date Calculation: How to Avoid Section 13 Tribunal Rejection in England | SignWise