The property pages of the self-assessment return ask for a small number of figures, and every one of them comes from a record a landlord either kept through the year or reconstructs in January. This page is for the UK buy-to-let landlord gathering the figures for self assessment property income: what the income figure is, which expenses go where, why finance costs are treated separately, and how the rent roll and the year's accounts produce each number so the return, or the accountant, gets figures rather than estimates. It describes the figures, not which box to fill; the tools apply the published rates to what you enter and never decide what you may claim. The landlord accounts tool on this site organises the year in these categories.
The income figure
Rental income is normally the rent received in the tax year, from the sixth of April to the fifth of April, across all your let properties. It comes straight from the rent roll's received column totalled for the year. Rent that fell due but was not paid is arrears, kept separately, not income. Other receipts connected with the letting, such as a fee charged to a tenant, are income too and belong in the record as they arrive.
The expense categories
The return groups allowable expenses into a handful of categories: rates, insurance and ground rents; property repairs and maintenance; legal, management and professional fees; costs of services provided; and other allowable expenses. A landlord who records each cost in one of those categories as it is paid has the expense figures ready at year end without sorting a year of receipts. Whether a borderline cost is allowable or capital is a question for the guidance or your accountant; the record's job is to hold the cost with its date and category so the question can be answered.
Finance costs, kept apart
Mortgage interest and other finance costs on a residential letting are not deducted as an expense. Relief is restricted to the basic rate of Income Tax, at 20%, and given as a reduction from the tax bill. The return therefore asks for finance costs as their own figure, separate from the expenses above, and a landlord who has recorded interest as an ordinary expense will have to unpick it. The rental income tax calculator on this site applies the restriction to the interest you enter, and the accounts tool keeps interest in its own column.
The profit, and the tax it attracts
Income less allowable expenses is the rental profit, added to your other income and taxed at your marginal rate: 20% on taxable income between the Personal Allowance of £12,570 and £50,270, 40% up to £125,140 and 45% above that, with the basic-rate reduction for finance costs then taken off the bill. The tax calculator here works the estimate from your figures so the January bill is not a surprise.
Producing the figures from the record
Rent roll received column, totalled for the tax year: income. Costs by category, totalled: expenses. Interest, totalled: finance costs. Arrears at the fifth of April: for the accountant, not the return. A landlord who keeps the four through the year produces the return's figures in an hour; RentRollDesk Pro, at £9 per month for every property, keeps them per property with the year-end export, and the free accounts tool here does the arithmetic without an account.
Questions people ask about self assessment property income
Is self assessment property income the rent due or the rent received?
Normally the rent received in the tax year. Unpaid rent is arrears, kept separately.
Where does mortgage interest go on self assessment property income?
As a separate finance-cost figure, relieved at the basic rate as a reduction from the tax bill, not as an expense against income.
Do I need an accountant for the property pages?
For borderline questions about what is allowable, or for a larger portfolio, many landlords use one. Either way the figures come from the record, and the tools here produce them.