Self Assessment Tax Return UK —
Every Relief Claimed, Filed On Time

Most self-employed individuals and sole traders significantly under-claim expenses. Allowable expenses include: home office costs (flat rate or actual), vehicle costs (business mileage or actual), equipment and tools, professional subscriptions, training, accountancy fees, marketing, travel and subsistence, business insurance and bank charges. We review every category systematically to ensure nothing is missed.

Many first-time Self Assessment filers are shocked to receive a bill for 150% of their expected tax — because HMRC requires payment on account of the following year’s tax alongside the actual tax owed. We prepare you for this by calculating your payment on account well in advance and advising on whether a reduction claim is appropriate if your income is expected to fall.

Higher and additional rate taxpayers who contribute to a pension can claim additional tax relief via Self Assessment — up to 45% effective relief on every pound contributed. Basic rate relief is claimed at source, but higher rate relief must be claimed on your return. This is one of the most frequently missed reliefs for higher earners.

You must register for Self Assessment by 5 October following the tax year in which you first had taxable income. For example, if you became self-employed in 2023/24, you had until 5 October 2024 to register. Late registration carries a penalty — and HMRC can assess tax, interest and penalties for the entire period of non-registration. We register new clients immediately and ensure no penalties arise.

The online Self Assessment filing deadline is 31 January following the end of the tax year. So for the 2023/24 tax year (ending 5 April 2024), the online filing deadline is 31 January 2025. The paper filing deadline is earlier — 31 October. Missing the online deadline triggers an automatic £100 penalty from day one, regardless of whether any tax is owed.

Britvex Self Assessment fees start from £149 for straightforward returns and rise depending on complexity. All fees are fixed and agreed upfront before we start work. For comparison, the average UK accountant charges £150-£350 for a basic return and up to £600+ for complex returns — and many charge hourly rates that increase unpredictably. Our fees include everything — tax advice, preparation, submission and a year of HMRC correspondence.

Allowable expenses depend on your income type. Self-employed individuals can claim all expenses incurred wholly and exclusively for the purpose of the business. Common claims include: office costs (rent, utilities, supplies), travel (business mileage at HMRC rates or actual vehicle costs), equipment and tools, professional fees and subscriptions, training, advertising and marketing, insurance and bank charges. Landlords can claim mortgage interest (subject to Section 24 restriction), letting agent fees, repairs and maintenance, insurance, service charges and furniture replacement allowance.

Yes — individuals with income above £100,000 must file a Self Assessment return, even if they are employed and PAYE is operated on their salary. This is because the personal allowance is tapered for incomes above £100,000, creating a complex tax position that PAYE cannot handle accurately. We prepare these returns specifically to optimise the position — including pension contributions and Gift Aid to reduce adjusted net income and restore the personal allowance.

Missing the 31 January deadline triggers an automatic £100 penalty — even if your return shows no tax to pay. After 3 months, a further £10/day penalty applies (up to £900). After 6 months, an additional penalty of 5% of the tax owed (minimum £300). After 12 months, a further 5% (minimum £300). On top of penalties, HMRC charges interest on unpaid tax from 1 February. We file all returns well before the deadline and have never incurred a late filing penalty for any client.