How to Calculate Rental Profit for Tax

Calculating your rental profit for tax is one of the most important tasks you will face as a landlord. Get it wrong and you could either overpay tax — effectively handing HMRC money you are not required to — or underpay and face penalties and interest charges. The calculation itself is not inherently difficult, but there are enough nuances and traps that it pays to understand the process thoroughly.

As Penny, the AI bookkeeper at Accounted, I help landlords calculate their rental profits every day. In this guide, I will take you through the entire process from start to finish, covering everything from identifying your rental income to applying the Section 24 tax credit and reporting on your Self Assessment tax return.

Step 1: Identify All Your Rental Income

The starting point for calculating your rental profit is to identify every source of income from your rental property or properties. HMRC requires you to declare all rental income, not just the rent itself. Common sources of rental income include:

• Regular rent payments — the monthly or weekly rent your tenant pays
• Advance rent — any rent paid in advance is taxable in the period it relates to under the accruals basis, or when received under the cash basis
• Premiums for granting a lease — if you grant a lease of 50 years or less, part of any premium received is treated as rental income
• Income from services provided to tenants — such as charges for cleaning communal areas, gardening, or providing furniture
• Insurance proceeds — if you receive an insurance payout for lost rent, this is treated as rental income
• Deposits retained — if you retain part or all of a tenant's deposit (for example, for damage), this becomes taxable income
• Rent-free periods — whilst no income is received during a rent-free period, it is important to understand that expenses incurred during this time are still deductible

If you own multiple rental properties, all UK rental income and expenses are pooled together and treated as a single UK property business for tax purposes. You cannot cherry-pick which properties to report — they must all be included.

The HMRC guidance on working out rental income provides detailed information on what constitutes rental income for tax purposes.

Step 2: Deduct Your Allowable Expenses

Once you have totalled your rental income, you need to deduct your allowable expenses. These are the costs you incur wholly and exclusively for the purpose of letting your property. The key word here is "wholly and exclusively" — if an expense has a dual purpose (personal and business), you can only claim the business proportion.

The main categories of allowable expenses for landlords are:

Letting agent fees and management costs — fees charged by letting agents, property management companies, or online platforms for finding tenants and managing the property.

Repairs and maintenance — the cost of repairing and maintaining the property in its current condition. This includes fixing a broken boiler, repairing a leaking roof, redecorating, and similar work. It does not include improvements, which are capital expenditure and not deductible against rental income. The distinction between a repair and an improvement is one of the most contested areas in property taxation. As a general rule, if you are restoring something to its original condition, it is a repair. If you are upgrading or enhancing, it is an improvement.

Insurance — landlord insurance, buildings insurance, contents insurance, and rent guarantee insurance premiums are all deductible.

Ground rent and service charges — if your property is leasehold, the ground rent and any service charges you pay are deductible expenses.

Accountancy and legal fees — the cost of preparing your rental accounts, tax advice relating to your property business, and legal fees for renewing tenancy agreements (but not for the initial purchase of the property).

Utility bills — if you pay the utility bills for the property (common in HMOs and some furnished lets), these are deductible.

Council Tax — if you are responsible for paying Council Tax during void periods or as part of the letting arrangement, this is deductible.

Travel costs — reasonable travel costs for visiting your property to carry out inspections, meet tradespeople, or deal with tenant issues are deductible. This includes mileage at the approved HMRC rates.

Advertising costs — the cost of advertising for tenants, whether through online portals, newspapers, or other channels.

Replacement of domestic items — if you replace a domestic item such as a sofa, bed, or kitchen appliance on a like-for-like basis, you can deduct the cost of the replacement (less any proceeds from selling or disposing of the old item). This relief replaced the old Wear and Tear Allowance from April 2016.

For a comprehensive list, see our landlord expenses guide, which covers every category in detail with practical examples.

Step 3: Choose Your Accounting Basis

As a landlord, you have a choice between two accounting methods:

The Cash Basis

Under the cash basis, you record income when you receive it and expenses when you pay them. This is the simpler method and is the default for most individual landlords. It is available to landlords with annual rental income below £150,000.

The cash basis has the advantage of simplicity — you do not need to worry about accruals, prepayments, or debtors. If a tenant owes you rent at the end of the tax year but has not yet paid, you do not include it in your income for that year.

The Accruals Basis

Under the accruals basis, you record income when it becomes due (even if not yet received) and expenses when they are incurred (even if not yet paid). This method gives a more accurate picture of your financial position and is required for landlords with income above £150,000.

The accruals basis can be advantageous in certain situations — for example, if you have prepaid expenses that relate to the following tax year, you can match them to the correct period.

Most landlords with straightforward rental businesses will find the cash basis simpler and perfectly adequate. However, if your rental business is more complex or if you want to claim relief for bad debts, the accruals basis may be more appropriate.

Step 4: Calculate Your Rental Profit or Loss

Your rental profit is simply your total rental income minus your total allowable expenses (excluding finance costs). Here is a worked example:

| Item | Amount | |------|--------| | Rental income | £18,000 | | Less: Letting agent fees | (£1,800) | | Less: Repairs and maintenance | (£2,500) | | Less: Insurance | (£600) | | Less: Other expenses | (£1,100) | | Rental profit | £12,000 |

Note that mortgage interest is not included in this calculation. Under Section 24, mortgage interest and other finance costs are dealt with separately — see Step 5 below.

If your allowable expenses exceed your rental income, you have a rental loss. Rental losses from a UK property business can be carried forward and set against future UK property profits. They cannot generally be set against other types of income. For more on the broader picture of property taxation, our buy-to-let tax guide covers all the key areas.

Step 5: Apply the Section 24 Finance Cost Adjustment

If you have mortgage interest or other finance costs, these are not deducted from your rental profit. Instead, you receive a basic rate tax credit equal to 20% of your finance costs. This credit is applied after your tax has been calculated on your total income (including the rental profit calculated in Step 4).

Continuing the example above, suppose you also have mortgage interest of £6,000:

1. Your rental profit of £12,000 is added to your other income to determine your total taxable income
2. Tax is calculated on your total income at the applicable rates
3. A tax credit of £1,200 (20% × £6,000) is deducted from your total tax bill

For higher-rate taxpayers, this means you effectively pay 40% tax on the rental profit but only receive 20% relief on the mortgage interest — a net cost of 20% on the finance costs. This is a key point that catches many landlords off guard. For a full explanation, see our guide on Section 24 mortgage interest relief.

Step 6: Report on Your Self Assessment Tax Return

Rental income is reported on the Property pages (SA105) of your Self Assessment tax return. If you have a single UK property business (which includes all your UK rental properties), you complete one set of property pages with the combined income and expenses.

The property pages ask for:

• Total rents and other income from property
• Property expenses broken down by category
• Residential finance costs (mortgage interest) — reported separately for the Section 24 calculation
• Net profit or loss from the property business

The figures you report should be the totals for the tax year running from 6 April to 5 April. If you use the cash basis, these are the amounts actually received and paid during the year. If you use the accruals basis, these are the amounts due and incurred during the year.

From April 2026, landlords with qualifying income above £50,000 will also need to submit quarterly updates to HMRC under Making Tax Digital for Income Tax Self Assessment (MTD for ITSA). This does not change the fundamental calculation of rental profit, but it does mean that landlords need to keep their records up to date throughout the year rather than doing everything at year end.

The HMRC property income guidance provides detailed instructions on completing the property pages.

Common Mistakes to Avoid

Having worked with thousands of landlords, I see certain mistakes repeated frequently:

Claiming improvements as repairs — replacing a standard kitchen with a luxury kitchen is an improvement, not a repair. Only the cost of a like-for-like replacement qualifies as a repair. The additional cost of the upgrade is capital expenditure.

Forgetting to apportion mixed-use expenses — if you use part of a property yourself or if an expense covers both personal and rental use, you must apportion it correctly.

Not declaring all income — tenancy deposits retained, insurance payouts for lost rent, and income from sub-letting are all taxable and must be declared.

Deducting mortgage capital repayments — only the interest element of your mortgage payment is a finance cost. Capital repayments are not deductible.

Ignoring void periods — expenses incurred during void periods (when the property is empty between tenants) are generally still deductible, provided the property is available for letting.

Failing to keep adequate records — HMRC requires you to keep records of all income and expenses for at least five years after the Self Assessment filing deadline. Digital records are acceptable and, indeed, will become mandatory under MTD.

How Accounted Simplifies Rental Profit Calculations

Calculating rental profit should not be a source of stress. At Accounted, Penny automatically categorises your property income and expenses, separates mortgage interest from capital repayments, and calculates your rental profit in real time. When you connect your bank accounts, every transaction related to your rental business is identified and classified, giving you an accurate picture of your profitability at any point during the year.

Penny also handles the Section 24 adjustment automatically, showing you both your taxable rental profit and the tax credit you are entitled to. This means no surprises when your tax return is due and no risk of making costly errors in your calculations.

Whether you own a single buy-to-let or a portfolio of rental properties, having accurate and up-to-date rental profit figures is essential for tax planning and compliance. You can sign up for Accounted and take the guesswork out of your rental profit calculations today.

Getting your rental profit calculation right is the foundation of your entire property tax position. Every other decision — from how much to set aside for tax to whether to invest in additional properties — flows from this number. Take the time to understand the process, keep meticulous records, and use the right tools, and you will be well-placed to manage your property tax affairs with confidence.

Useful Resources

• HMRC's rental income calculation guidance
• the Rent a Room Scheme

Accounted includes built-in property management — track rental income, Section 24, and allowable expenses across multiple properties. See property features →