Self Assessment Tax Return Guide

Who Must File?

Not everyone pays tax automatically through PAYE. You must file a Self Assessment return if, in the last tax year (6 April to 5 April), you were:

• A sole trader with gross income over £1,000
• A partner in a business partnership
• Earning over £100,000 total taxable income (until 2022/23) or £150,000 (from 2023/24)
• Earning untaxed income (e.g., tips, commission) over £2,500
• A landlord with rental income over £2,500 (or £10,000 gross)
• Claiming Child Benefit and you or your partner earn over £50,000 (High Income Child Benefit Charge)
• Earning income from abroad

The Tax Calendar

Missing a deadline results in immediate penalties. Mark these dates for the 2023/24 tax year:

How to Register

If you've never filed before, you must register to get your Unique Taxpayer Reference (UTR). This is a 10-digit number essential for filing.

• Sole Traders: Register via gov.uk as "self-employed".
• Non-Traders: Register using form SA1 (e.g., for rental income).
• Partners: Register using form SA401.

After registering, you'll receive your UTR by post within 10-15 days. You will then need to set up a Government Gateway account to file online.

What to Declare

You must report ALL taxable income, not just self-employment earnings. This includes:

• Employment wages (P60/P45 figures)
• Dividends
• Bank interest
• Pension income
• State benefits (some are taxable)

Allowances (2023/24)

Allowable Business Expenses

You only pay tax on profits (Income - Expenses). Expenses must be "wholly and exclusively" for business purposes.

• Office costs: Stationery, phone bills (business % only)
• Travel: Fuel, parking, train fares (not commuting)
• Clothing: Uniforms or protective gear only (not regular suits)
• Staff costs: Salaries, subcontractor fees
• Financial: Insurance, bank charges, accountant fees
• Advertising: Website costs, flyers

Working from Home

You can claim a portion of household bills (heating, lighting, internet) based on:

1. Simplified Expenses: Flat rate based on hours worked (e.g., £10/month for 25-50 hrs).
2. Actual Costs: Calculating the precise proportion of rooms/time used (complex but accurate).

What are Payments on Account?

This is often a shock for new traders. If your tax bill is over £1,000, HMRC asks you to pay for next year's tax in advance, in two installments.

If you expect your income to drop next year, you can ask HMRC to reduce these payments.

The Process

Once logged into Government Gateway:

• Check your personal details are correct.
• Answer the "Tailor your return" questions (e.g., "Were you self-employed?", "Did you receive interest?"). This filters the forms you see.
• Fill in the turnover and expenses figures.
• Double-check calculations.
• View the tax calculation summary.
• Submit the return and save the submission receipt/PDF.

Late Filing Penalties

Reasonable Excuses

You can appeal fines if you have a "reasonable excuse," such as:

• Death of a partner/close relative
• Unexpected hospital stay
• Computer failure whilst filing (with evidence)
• Fire/Flood/Theft

"I forgot" or "I found it difficult" are NOT accepted excuses.