Short answer: for a let home, each gas appliance and flue must be checked within 12 months of the last check. A check done in the 2 months before that deadline counts as done on the deadline, so the next one is due 12 months after the original date. An earlier check resets the date. The rule is regulation 36A of the Gas Safety (Installation and Use) Regulations 1998.
Work out the next due date
Result
| Next check due by | |
|---|---|
| Check from this date to keep the anniversary | |
| Latest date for a once-only alignment check |
| What happens | |
|---|---|
| The check after that is due by |
The calculator does the date arithmetic. It does not decide whether regulation 36 applies to a building. Nothing you type is stored.
Who the rule applies to
Regulation 36 is a duty on landlords. It covers "relevant premises": premises or any part of premises occupied for residential purposes, for money or money's worth, under a lease or a licence. For this regulation a "lease" means a lease for a term of less than 7 years, a periodic tenancy, or a statutory tenancy arising from either (reg 36(1)). For those premises the landlord must:
- have each appliance and flue checked for safety within 12 months of being installed, and at intervals of not more than 12 months since the last check (reg 36(3)(a));
- for a new lease, have each appliance and flue checked within the 12 months before the lease starts, or within 12 months of installation if that is later (reg 36(3)(b));
- use a business on the Gas Safe Register for the check (reg 36(4));
- keep the record until there have been two further checks, and give existing tenants a copy within 28 days of the check (reg 36(3)(c) and (6)(a)).
Commercial premises are different
In a shop, restaurant, office or school, regulation 35 makes the employer or self-employed person keep the gas appliances, pipework and flues they control in a safe condition. GSIUR sets no fixed interval and no record format for those premises, so regulation 36A has no legal effect there: the manufacturer's instructions and the maintenance contract set the cycle. HSE asks employers to make sure gas appliances are maintained "by a competent person and in line with manufacturers' instructions and appropriate standards". A boiler in a shop that also serves a let flat above is a relevant gas fitting when it is installed in a part of the building in which the landlord has an interest, or is owned or controlled by the landlord (reg 36(1)), so regulation 36, including the 12-month rule, applies to it. Only appliances used exclusively in the non-residential part are left out. Our guide to gas safety law in commercial premises sets out which duty covers which appliance.
The 2-month rule, word for word
Regulation 36A was added from 6 April 2018 by the Gas Safety (Installation and Use) (Amendment) Regulations 2018. It says:
- a check completed "within the period of 2 months ending with the deadline date" is "treated ... as having been made on the deadline date" (reg 36A(1));
- the deadline date is "the last day of the 12 month period within which the check is or was required to be made" (reg 36A(4));
- the landlord may instead have the check done "within the 2 month period beginning with the deadline date", but only once for each appliance or flue, and only to line up its deadline with another appliance or flue in the same premises (reg 36A(2) and (3)).
HSE puts it this way: the check can be carried out "up to 2 months before the date the check needs to be carried out but still retain the original deadline date as if the check had been carried out exactly 12 months after the previous check".
How the calculator counts months
| Step | Rule | Example |
|---|---|---|
| Deadline | The same date 12 months after the last check, or the due date on the record if you enter one | Last check 15 March 2026: due by 15 March 2027 |
| Window that keeps the anniversary | From the day after the same date 2 months before the deadline, up to the deadline | Deadline 15 March 2027: 16 January to 15 March 2027 |
| Check inside the window | Next deadline is 12 months after the old deadline | Check on 20 February 2027: next due by 15 March 2028 |
| Check before the window | Next deadline is 12 months after the day of the check | Check on 10 January 2027: next due by 10 January 2028 |
| Check after the deadline | Late, unless it is the once-only alignment check within 2 months; either way the next deadline is 12 months after the check | Check on 16 March 2027: late, next due by 16 March 2028 |
| Months of different lengths | Where the same date does not exist, the calculator uses the last day of the month, which is the earlier date | Last check 29 February 2024: due by 28 February 2025 |
Where months have different lengths, the regulations do not spell out the count. The calculator always takes the earlier of the possible dates, so it never shows a deadline later than the law could require.
Worked example: a flat with a boiler and a gas fire
A landlord lets a flat with a boiler and a gas fire. The boiler was last checked on 15 March 2026, so it is due by 15 March 2027. The gas fire was fitted later and last checked on 20 January 2026, so it is due by 20 January 2027. The landlord wants one visit a year.
| Appliance | Due by | Checked on | Why it is allowed | Next due by |
|---|---|---|---|---|
| Boiler | 15 March 2027 | 15 March 2027 | Inside the 12 months | 15 March 2028 |
| Gas fire | 20 January 2027 | 15 March 2027 | Once-only alignment check, within 2 months beginning with 20 January 2027 (up to 19 March 2027) | 15 March 2028 |
From then on both appliances share one date, and any visit from 16 January to 15 March each year keeps it. The gas fire cannot use the alignment option again.
Who does what
- The landlord makes sure each check happens in time, keeps the records and gives tenants their copies. The duty cannot be passed to the tenant, except for appliances in a part of the premises used for non-residential purposes (reg 36(10)).
- The Gas Safe registered business carries out the check, which must include at least the examination in regulation 26(9): flue, combustion air, operating pressure or heat input (or combustion performance), and safe functioning (reg 36(9)).
- The managing agent or maintenance contractor books the visit in the window and sends the record on.
What to record
Regulation 36(3)(c) lists what the record must include:
- the date of the check, and the address of the premises;
- the name and address of the landlord, or the agent;
- a description and the location of each appliance or flue checked;
- any safety defect found, and any remedial action taken;
- confirmation that the check complies with regulation 36(9);
- the name and signature of the person who did the check, and the Gas Safe registration number of that person or their employer.
Add the deadline that applies after this check, so the next visit is booked in the window.
Next due dates in Field Suite
- Landlord gas safety record: the form library has a ready-made record for domestic lets built on regulation 36(3). When it is completed, the next due date is worked out with the 2-month rule: a check in the 2 months before the last record's due date keeps that date.
- Coming due: the forms page lists certificates coming due in the next 60 days, with a button to book the next visit as a job with the form ready.
- Sign-off: with the People module on, the form can require an in-date Gas Safe qualification recorded in People and checked by an owner or admin before the engineer signs it off.
- Contracts: for commercial sites, a contract schedules the visit in whole months, for example every 12 months, and creates the job a set number of days before it is due.
See planned maintenance software, prices, or book a demo.
Field Suite is job management software. The landlord and the Gas Safe registered business remain responsible for the check and the record.
Questions
Can I have the check done 3 months early and keep the date?
No. Only a check in the 2 months ending with the deadline keeps it. A check earlier than that starts a new 12 months from the day of the check.
Does the 2-month rule apply to a shop or an office?
Regulation 36A only changes the regulation 36 deadline, which applies to let residential premises. Workplaces fall under regulation 35, which has no fixed interval. A maintenance contract can still use a yearly cycle.
What if the record shows a due date?
Enter it in the second box. That matters when the last check was itself done early and kept an older anniversary.
Is a check one day after the deadline a breach?
Regulation 36(3)(a) asks for intervals of not more than 12 months. The only exception is the once-only alignment check in regulation 36A(2), which must be made to line up deadlines in the same premises.
Sources
- Gas Safety (Installation and Use) Regulations 1998, regulation 36. https://www.legislation.gov.uk/uksi/1998/2451/regulation/36
- Gas Safety (Installation and Use) Regulations 1998, regulation 36A. https://www.legislation.gov.uk/uksi/1998/2451/regulation/36A
- Gas Safety (Installation and Use) Regulations 1998, regulation 35. https://www.legislation.gov.uk/uksi/1998/2451/regulation/35
- Gas Safety (Installation and Use) Regulations 1998, regulation 26. https://www.legislation.gov.uk/uksi/1998/2451/regulation/26
- HSE, Gas safety: landlords and letting agents. https://www.hse.gov.uk/gas/domestic/faqlandlord.htm
- HSE, Gas safety for employers. https://www.hse.gov.uk/gas/employers.htm
Last checked: 5 November 2026 against the sources above.
Checked in detail: GSIUR 1998 regs 26, 35, 36 and 36A read again on legislation.gov.uk (latest revised text, no outstanding effects on reg 36A; reg 36A inserted 6.4.2018 by SI 2018/139), HSE pages for landlords (faqlandlord) and employers re-read.
Field Suite is job management software for UK building services firms, not a consultancy. Your own risk assessments, contracts and advisers decide what applies to your work. Spotted a mistake? Email info@fieldsuiteapp.com and we correct it.