How to Fill In the SA105 for 2025-26: Every Box and a Worked Example

The SA105 is the UK property section of a Self Assessment tax return: the pages where a landlord reports rent, costs and mortgage interest. For the 2025-26 tax year (6 April 2025 to 5 April 2026) it is the form HMRC prints as SA105 2026. A paper return must reach HMRC by 31 October 2026. Online, the deadline is 31 January 2027, which is also the day the tax is due.

A landlord with one or two ordinary lets fills in about a dozen boxes: 1, 20, 24 to 29, 36, 38, 40 and 44. In the worked example below, one house with £12,100 of rent, £3,501 of costs and £5,100 of mortgage interest ends with £699.80 of tax for a basic-rate taxpayer. This guide takes the boxes in turn, then follows that landlord's year through the form to the tax at the end.

Every box number below was read on the 2026 form and its notes, and every rule on GOV.UK, on 25 October 2026. The numbers belong to the paper form, and the notes use them too.

Not tax advice. The tax figures are for a taxpayer outside Scotland. Where your case is unusual, use an accountant.

The boxes most landlords use

The form runs from box 1 to box 45. Boxes 5 to 19 are no longer in use and box 34 is not in use, so a 2026 form that looks short is complete. These are the boxes an ordinary residential let reaches:

Two rules run across the whole form. If you own the property with someone else, every box takes only your share (the box 3 notes). And if your property income before expenses is below £90,000, the notes let you put your expenses as one total in box 29 instead of splitting them over boxes 24 to 29. Mortgage interest on a home stays out of that total and goes in box 44.

One landlord's 2025-26, box by box

The example is invented but ordinary. One terraced house in England, let unfurnished with a free-standing washing machine supplied, owned in one name with an interest-only mortgage. The landlord is employed on £30,000 a year, so the salary uses up the personal allowance. A managing agent collects the rent for 12% including VAT. The figures are on the cash basis, which is the default for property income up to £150,000, so box 20.2 (traditional accounting) stays empty.

Rent of £1,100 a month came in for 11 months. The house stood empty in September 2025 while it was repainted between tenants.

Boxes 26 and 28 stay empty: the mortgage is on a home, and the landlord provides no services such as cleaning. The repainting is a repair because it restores the house between tenants, which GOV.UK names as an allowable repair.

Box 44 takes the interest for the tax year. If the lender's yearly statement runs to 31 December, or to the mortgage's anniversary, add up the interest month by month from 6 April 2025 to 5 April 2026 instead of copying the statement's total.

From the boxes to the profit

The notes give a working sheet for boxes 38 and 41. Income first, then the deductions:

M is positive, so £8,599 goes in box 38. There is no loss from earlier years, so box 39 is empty and box 40, the taxable profit, is also £8,599. The £5,100 of interest is in none of these lines. It goes only in box 44.

The tax it leads to

For 2025-26 the personal allowance is £12,570. Outside Scotland, income above it is taxed at 20% up to £50,270 and at 40% from there to £125,140. The salary uses the allowance, so the whole profit is taxed at 20%.

£699.80 is under £1,000, so on GOV.UK's rule there are no payments on account towards the next year. It is also under £3,000, and the landlord already pays tax through PAYE. If the return goes in online by 30 December 2026, HMRC collects the tax through the tax code on the salary, unless the return asks it not to. GOV.UK lists the exceptions: not enough PAYE income to collect it from, more than half of that income going in tax, or more than twice the tax you normally pay.

On a £60,000 salary the same profit is all taxed at 40%: £3,439.60, less the same £1,020, leaves £2,419.60. Before Section 24 the interest came off the profit and saved 40% of £5,100, which is £2,040. Now it saves £1,020. On that salary the profit also takes adjusted net income above £60,000, where the High Income Child Benefit Charge starts. If you or your partner gets Child Benefit, that charge can apply as well.

Property allowance or expenses: box 20.1

The property allowance takes £1,000 off your property income in place of your actual costs. If your property income for the year is £1,000 or less, it is covered and you need not report it, unless one of the exclusions below applies. Above £1,000 you choose one of two routes:

• The allowance: £1,000 in box 20.1, nothing in box 44, and boxes 24 to 29, box 30 and boxes 32 to 36 left empty, as the notes list them
• Your expenses: the boxes filled in as above, and box 20.1 left empty

The allowance and the mortgage interest reduction do not mix. GOV.UK says you cannot use the property allowance if you claim the tax reducer for finance costs on a residential property. Nor can it be used on Rent a Room income, or at all in a year when any of your property income comes from a company you or someone connected to you owns or controls, a partnership where you or someone connected to you is a partner, or your employer or your spouse's or civil partner's employer. Joint owners can each use it against their own share.

For the example landlord the choice is plain:

Expenses win by £1,520.20. With no mortgage, the allowance wins only when the year's allowable costs come to less than £1,000. With a mortgage, work the tax out both ways, because choosing the allowance also gives up the 20% reduction on the interest.

Box 44: mortgage interest as a 20% reduction

Since April 2020, finance costs on a home you let come off your tax, not your profit. That is the Section 24 change, and box 44 is where it starts. Box 44 takes:

• interest on the mortgage, and on other loans for the let, including a loan to buy furnishings
• overdraft interest for the let
• fees and other costs of getting or repaying a mortgage or loan

Never the capital part of a repayment mortgage: only the interest counts. Interest on a loan for a shop, office or other non-residential property you let goes in box 26 instead, and comes off the profit in full. A loan for both kinds is split on a reasonable basis.

The reduction is 20% of the lowest of three figures (GOV.UK):

1. 1the finance costs: box 44 plus box 45
2. 2the property profits for the year, after any losses brought forward
3. 3your income above the personal allowance, leaving out savings and dividend income

For the example landlord the lowest is the £5,100 of interest, so the reduction is £1,020. At the basic rate that is the same tax as deducting the interest gave before Section 24; the difference shows at 40%, as the £60,000 salary above shows. Had the house stood empty for longer and the profit been £3,000, the reduction would have been 20% of £3,000, which is £600, and the other £2,100 would go in box 45 on next year's return. The reduction never creates a refund.

The Section 24 calculator runs the same sums on your own figures, and Section 24 explained covers why a higher-rate landlord pays more. For the rates from April 2027, see landlord tax rates and the April 2027 rise.

Boxes 1 to 23: the details and the income

Boxes 1 to 4. The number of properties; an X if all your property income stopped in 2025-26 and none is expected in 2026-27 (then check whether you need the Capital Gains Tax summary pages); an X for property let jointly; and an X for Rent a Room relief where the rents were £7,500 or less (£3,750 if let jointly). A landlord whose only letting is a room under that limit stops there; lodger or tenant has the rules. If you own the property with your spouse and live together, HMRC taxes your shares equally unless you have a different share and send Form 17; joint owners and Form 17 explains.

Box 20. Rent and everything else the property brings in, such as money for the use of furniture or a council grant towards repairs. Put the full rent, before the agent's fee. A pay-out from your own rent guarantee policy goes here too. On the cash basis it is what you received between 6 April 2025 and 5 April 2026. On traditional accounting (an X in box 20.2) it is the rent for 2025-26, including rent for that year paid after 5 April 2026, but not rent paid in advance for 2026-27.

The furnished holiday lettings rules ended in April 2025, so a holiday let's income now goes in box 20 with the rest of your UK property income.

Box 21. Only for a non-resident landlord whose agent or tenant took tax off the rent under the Non-Resident Landlord Scheme. Box 20 still takes the rent before the tax came off.

Boxes 22 and 23. Rare on a residential let. A premium for a lease of up to 50 years is partly income: the working sheet in the notes keeps 2% of it out for each complete year of the lease after the first, and box 22 takes the rest. Box 23 takes a payment you received as an inducement to take on a property interest.

Boxes 24 to 29: the running costs

Only running costs go here. Buying, selling, improving or altering the property, its equipment or its furniture is capital and stays out.

Box 24. Rent you pay on a lease of the property you let, business rates, water rates and council tax you paid, property and contents insurance, insurance against loss of rent, and ground rents. The notes do not name service charges on a leasehold flat. GOV.UK lists them beside ground rents as an allowable cost, and LetCompliance files them in box 24 with the ground rent.

Box 25. Repairs and maintenance: painting, damp treatment, roof repairs, repairs to furniture and to machinery supplied with the property. A repair restores. Replacing a part with its nearest modern equivalent is still a repair if the improvement is incidental to the repair, and GOV.UK's example is double glazing in place of single. Like-for-like baths, basins and toilets count too. Adding something the property did not have before is capital. If insurance or a deposit you kept paid for part of a repair, claim only the part you paid.

Box 26. Finance costs on non-residential property only. For a home, see box 44.

Box 27. Management fees paid to an agent for rent collection, advertising and administration; legal fees for renewing a lease of less than 50 years; fees to evict a tenant in order to re-let. Not the costs of a first letting for more than a year, planning permission, or registering the title when you buy.

Box 28. Services you provide to the tenant, such as communal hot water, gardening or cleaning, with any wages. Money the tenant pays you for them goes in box 20.

Box 29. Everything else allowable: stationery, phone calls and business travel (the notes point to HMRC's flat mileage rates), and, on traditional accounting only, rent written off as a bad debt. On the cash basis unpaid rent never reached box 20, so there is nothing to write off.

What counts and what is capital, item by item, is in the full list of allowable expenses by SA105 box.

Boxes 30 to 45: reliefs, losses and the profit

Box 30. The private part of any cost in boxes 24 to 29. The notes' example: a full year's insurance in box 24 on a property you used yourself for 4 months, so the 4 months' cost goes in box 30.

Boxes 31 to 35. A balancing charge (box 31) and capital allowances (boxes 32, 33, 33.1, 33.2, 34.1 and 35; box 34 is not in use). On an ordinary residential let these are often empty: the notes say the Annual Investment Allowance cannot be claimed for equipment for use in a dwelling house. Box 33.1 is for electric charge points, box 33.2 for the Structures and Buildings Allowance in Freeport and Investment Zone tax sites, and box 34.1 for a new zero-emission car.

Box 36. Replacing a domestic item in a residential let: a bed, a free-standing wardrobe, curtains, carpets, a fridge, a television, crockery. It must replace an old item that is no longer available to the tenant, and the first furniture for a new let never counts. An upgrade is relieved only up to the cost of a like-for-like item: in GOV.UK's example a £550 sofa bed replaces a sofa, and only the £400 a sofa would cost counts. The relief works for unfurnished lets too, which is why the washing machine in the example is here and not in box 25.

Box 37. The Rent a Room exempt amount, £7,500 (or £3,750), when you put lodger income in box 20 and pay tax only on the excess.

Boxes 38 to 43. The working sheet's result: a profit in box 38, a loss in box 41. Box 39 sets earlier losses against the profit, starting from box 43 of your 2024-25 pages; box 40 is what is left; box 43 carries forward any loss still unused. Box 42, a loss set against your other income, is only for a loss from capital allowances or agricultural expenses, and the form says this will be unusual.

Deadlines, and what this return decides

• 31 October 2026: a paper return must reach HMRC by 11:59pm
• 30 December 2026: the online return, if you want tax under £3,000 collected through your tax code
• 31 January 2027: the online return, and payment of the tax

If this is your first return and you registered after 5 October 2026, HMRC sets a filing date 3 months from its letter, but the tax is still due by 31 January 2027. Your first tax return as a landlord covers registering and payments on account.

This return also decides Making Tax Digital. HMRC reads your 2025-26 return for the next threshold: if your self-employment and property income before expenses, which GOV.UK calls qualifying income, comes to more than £30,000, you need to use Making Tax Digital from 6 April 2027, with quarterly updates sent from software. The example landlord's £12,100 is well under it. Landlords who joined in April 2026 still file this 2025-26 return the usual way. The £30,000 threshold explains the test.

Keeping the year in boxes

Have the boxes ready before January. LetCompliance runs the let from one login: the advert, the tenancy, the rent and the repairs, with the money recorded as the let runs. On a paid plan, from £7.99 a month, each cost is filed against its property in its SA105 category, a photographed receipt becomes a draft expense to confirm, and the SA105 tax pack lays the year out in its boxes, from the rent in box 20 to the interest in box 44, at your share of a jointly owned property. It works out the taxable profit, the most the 20% reduction on this year's interest can be, and any loss carried forward. Your accountant can open the SA105 boxes, the ledger and the receipts through a read-only link, on every plan. A return on the SA105 is not sent from LetCompliance: you or your accountant send it, with the figures already in their boxes. Making Tax Digital comes with every paid plan: LetCompliance is recognised by HMRC for Making Tax Digital and sends the quarterly updates for your UK property income from the same records.