How to Declare All Your Income on Self Assessment: Employment, Rental, Dividends and More (Part 3)

Quick answer

The self assessment return (SA100) is the core document, but for most people with multiple income streams, the real work happens across the supplementary pages. Employment income, rental income, dividends, capital gains, and foreign income each have their own dedicated sections with specific boxes. The key to getting this right is knowing which document to use as your source for each income type, and understanding a few important rules — particularly that rental mortgage interest is now a tax credit rather than a deduction, and that crypto disposals are taxable events.

This is Part 3 of the UK Self Assessment From Scratch series. Part 2 covered registration and getting your UTR. This part explains exactly where each type of income goes on your return, what documents you need, and how to avoid common errors.

The return structure: SA100 and supplementary pages

The SA100 is the main self assessment tax return form. Everyone files an SA100. It covers personal details, residency status, total income summary, reliefs (pension contributions, Gift Aid), and your overall tax calculation.

Attached to the SA100 are supplementary pages for specific income types:

HMRC's online filing system only presents the pages relevant to the boxes you tick on the SA100 — so you will not accidentally complete irrelevant sections. However, you need to know which boxes to tick at the start to ensure the right supplementary pages load.

Employment income: SA102

Source documents

Your primary source is your P60 — the year-end summary your employer must issue by 31 May 2026 for the 2025/26 tax year. It shows:

• Total pay in the year (all taxable earnings including regular salary, bonuses, commission, and any PAYE expenses)
• Total income tax deducted
• Total National Insurance contributions (employee's NI)
• Your tax code as at 5 April 2026

If you worked for more than one employer during 2025/26, you need a P60 from your final employer and a P45 from any jobs you left during the year. Complete a separate SA102 page for each employment.

P11D for benefits in kind: if your employer provided taxable benefits — a company car, private health insurance, a gym membership, interest-free loans above £10,000, or living accommodation — you will receive a P11D by 6 July 2026. The total benefits value from your P11D is entered on SA102 (box 18: "Total amount of benefits from your employer"). These benefits are taxable as employment income.

Cross-checking via your Personal Tax Account

HMRC's Personal Tax Account at gov.uk/personal-tax-account will usually show the PAYE income your employer has reported via Real Time Information (RTI). Before filing, compare the SA102 figures you plan to enter against what HMRC already has. Small discrepancies can arise from timing (payroll submitted late in the year), redundancy payments, or PAYE errors. Where figures differ, use your P60 as the authoritative source and add a note in the "Additional information" box if needed.

Common employment income errors

• Forgetting a job held briefly: even a few weeks' employment generates taxable income and requires an SA102. A P45 from the employer is your source.
• Settling expenses claims: reimbursed expenses covered by a dispensation or HMRC's benchmark rates are not taxable. But if you received cash payments for expenses without a dispensation, those may be taxable — check with your payroll team.
• Share schemes: if you exercised share options or received company shares in 2025/26 (EMI, SAYE, SIP, CSOP, or unapproved options), these trigger income tax entries on SA102 or SA101. Your employer should provide an employment-related securities form — check this was reported on your P60 or a separate notification.

Self-employment income: SA103S or SA103F

The self-employment supplementary page covers all income from your trade. Part 4 of this series covers allowable expenses in full. For the income side:

• Box 8 (SA103S): total turnover — all money received in the year, including income yet to be invoiced (if using accruals basis) or all money actually received (if using cash basis)
• Box 9: deduct your allowable expenses (Part 4 covers these in detail)
• The difference is your taxable profit

If you use the cash basis of accounting (available to sole traders with turnover below £150,000), you enter money actually received and actually paid in the year. This is simpler for most small businesses.

If your turnover exceeded £85,000 in 2025/26, use SA103F (the Full version), which has more detailed expense boxes and also requires you to disclose your income and expenses in a structured format.

Rental income: SA105

Gross income and the allowable expense structure

SA105 requires you to enter gross rental income — the total rent you received before any deductions. Do not enter the net figure. Allowable expenses are entered in separate boxes and HMRC calculates the net profit:

Mortgage interest: the tax credit rule

This is the single most misunderstood aspect of rental income taxation. Since April 2020, mortgage interest is no longer deductible as an expense. Instead:

1. Enter the mortgage interest you paid in the year in the Finance Costs box on SA105.
2. HMRC calculates 20% of that figure.
3. The 20% amount is given as a tax reducer — a credit deducted from your tax bill, not from your income.

Why this matters: a higher-rate taxpayer can no longer use full mortgage interest to reduce their taxable rental profit. The 20% credit is worth the same to a basic-rate taxpayer as before, but a higher-rate taxpayer effectively loses relief on the portion above 20%.

Example: Marcus has rental income of £15,000 and mortgage interest of £8,000. Previously, he would have declared a profit of £7,000. Under the current rules, his taxable rental profit is £15,000 (minus other allowable expenses). He then receives a tax credit of £8,000 × 20% = £1,600 to offset against his income tax bill.

Furnished Holiday Lettings (FHL) abolished April 2025

The Furnished Holiday Lettings regime, which gave landlords preferential tax treatment for short-term holiday lets, was abolished from 6 April 2025. Properties that previously qualified as FHL are now taxed as standard residential rental properties under SA105. If you let a UK holiday cottage or Scottish short-term let, the FHL boxes are no longer available for 2025/26 onwards.

Dividends: SA101

What to declare

Enter all dividends received in 2025/26 from:

• UK companies (FTSE shares, investment trusts, smaller quoted companies)
• Overseas companies (foreign dividends — also requires SA106 entries for withholding tax credit claims)
• Collective investment schemes (OEICs, unit trusts) — use distribution statements from your fund manager
• Distributions from REITs

The Dividend Allowance is £500 for 2025/26. The first £500 of dividend income is tax-free for all taxpayers. Above £500:

Enter the total gross dividends in box 4 of SA101. HMRC's system applies the £500 allowance automatically.

Where to find dividend figures

• Company shares: dividend vouchers (posted or emailed by the company's registrar each time a dividend is paid)
• Broker/ISA platform: annual consolidated tax certificate — most platforms (Hargreaves Lansdown, AJ Bell, Interactive Investor) issue these by April or May. Note: dividends received within an ISA are completely exempt from tax and should NOT be included.
• Accumulation funds: income is "notionally distributed" even if you do not physically receive cash — check your fund manager's documentation for the "equalisation" amount and notional distribution figure.

Savings interest: SA101

When to declare

Savings interest is taxable above your Personal Savings Allowance:

• Basic-rate taxpayer (income to £50,270): first £1,000 of interest is tax-free
• Higher-rate taxpayer (income £50,271–£125,140): first £500 is tax-free
• Additional-rate taxpayer (income above £125,140): no allowance — all interest is taxable

If your total interest is below your PSA, you do not need to declare it. If it exceeds the PSA, you declare the gross total interest in SA101 — HMRC applies the allowance automatically.

Sources of taxable interest

• High-street savings accounts (easy access, fixed-rate bonds, regular savers)
• Current accounts paying interest
• Corporate bonds and gilts (the interest element — not the capital gain on gilts)
• Peer-to-peer lending platforms
• HMRC's own PAYE statement may show an estimated interest figure — cross-check against your bank statements

Interest received within an ISA is always exempt — do not include it. NS&I Premium Bond prizes are also exempt — do not include them. NS&I savings account interest is taxable and should be included.

Capital gains: SA108

Every disposal must be reported

A disposal occurs whenever you:

• Sell shares, funds, or investment trusts
• Sell a property that is not your main residence
• Give away an asset (treated as a sale at market value)
• Sell cryptocurrency
• Swap one cryptocurrency for another (each swap is a disposal)
• Receive compensation for an asset's loss or destruction

You must report all disposals where your total gains exceed the £3,000 Annual Exempt Amount (AEA). Note: even if gains are below the AEA, you must still report if your total disposal proceeds exceed four times the AEA (£12,000 for 2025/26).

SA108 key boxes

CGT rates for 2025/26:

The 60-day rule for UK residential property

If you sold a UK residential property in 2025/26 that was not your main home, you were required to:

1. Report the gain online via HMRC's "Report and pay Capital Gains Tax on UK property" service within 60 days of completion.
2. Pay the estimated CGT within the same 60-day window.

This is in addition to reporting the gain on your annual self assessment return. On SA108, HMRC credits you with the CGT you already paid in-year — so you are not taxed twice. But you must still complete SA108 to reconcile the position.

Foreign income: SA106

Any overseas income requires SA106. Common situations:

• Foreign employment income — if you worked partly overseas and paid overseas taxes, SA106 allows you to claim double tax relief.
• Overseas dividends — declare the gross dividend (before any foreign withholding tax) in the relevant SA106 boxes. You can claim credit for the foreign withholding tax deducted.
• Overseas rental income — declare gross income and deduct allowable expenses just as you would for UK property.
• Foreign pension income — most overseas pensions are taxable in the UK (depending on the double tax treaty with the relevant country). Enter the sterling equivalent of the annual pension received.
• Overseas bank interest — treated identically to UK interest; enter gross interest in SA106.

HMRC publishes approved exchange rates for converting foreign currency income to sterling. Use the rate on the date you received the income, or HMRC's annual average rate for consistency — the important thing is to use the same method throughout.

State benefits and pensions: what to include

The State Pension is paid gross — no tax is deducted at source. If your only income is the State Pension and it is below your Personal Allowance of £12,570, no tax is due. If you also have an occupational pension or employment income, HMRC usually adjusts your PAYE code to collect tax on the State Pension rather than requiring you to file.

Worked example: Maria's return

Maria earns £55,000 per year as a project manager at a tech company. She also has a buy-to-let flat, holds a stocks and shares ISA and a general investment account, and has a standard savings account.

Her 2025/26 income:

Pages Maria needs:

What Maria declares on each page:

SA102 (employment):

• Total pay from P60: £55,000
• Income tax deducted: per P60
• Benefits from P11D: none (she has no company benefits)

SA105 (rental):

• Gross rent received: £8,400
• Allowable expenses: £2,200
• Finance costs (mortgage interest): £2,100 entered in the dedicated Finance Costs box (not as a general expense)
• Net rental income before finance costs: £8,400 − £2,200 = £6,200
• HMRC calculates a 20% tax credit on the £2,100 mortgage interest: £420

SA101 (dividends):

• UK dividends: £800 gross
• £500 Dividend Allowance applied automatically — taxable dividend: £300 at 33.75% = £101.25 additional tax

Overall tax position summary (simplified):

• Total income: £55,000 (employment) + £6,200 (rental) = £61,200
• Dividend income above allowance: £300
• Income tax: broadly 40% higher rate on income above £50,270 = significant liability beyond PAYE
• Finance cost tax credit reduces bill by £420
• Her PAYE on the £55,000 salary will have been broadly correct — the additional tax is owed on the £6,200 rental profit and £300 excess dividends

Maria's self assessment return reconciles all these streams and produces the precise liability. Without a return, HMRC would only see her employment income and could not collect the correct tax on her rental and dividend income.

After entering all income: the tax calculation

Once you have entered all income across every relevant supplementary page, HMRC's online system calculates your tax liability automatically. Before submitting, review the summary screen carefully:

• Total income from all sources: does this match the sum of all your source documents?
• Total tax deducted at source: should match the tax shown on your P60(s) plus any other withholding taxes
• Net tax to pay (or overpayment): is this broadly what you expected given your income levels?
• Payments on account: if this is your first year or your income has increased significantly, check whether payments on account have been triggered (threshold: tax owed above £1,000 with less than 80% collected through PAYE)

Part 4 of this series covers the expenses side of the equation — particularly for self-employed people — and explains how to maximise your allowable deductions: How to Claim Allowable Expenses on Self Assessment: The Complete 2026 Guide.