Self Assessment

Self Assessment Tax Return Support

Self Assessment can feel complex, but it doesn’t have to be. At SBX Accountants, we take care of every step from preparing and checking your return to filing it securely with HMRC. Our Chartered Accountants explain your payments on account, apply all available reliefs, and make sure your figures are accurate and compliant.
The Self Assessment deadline for the 2024/25 tax year is 31 January 2026 for online submissions and 31 October 2025 for paper returns.

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Complete Service

What’s Included in Our Self Assessment Service

When you choose SBX Accountants, you get more than a simple tax return. Every Self Assessment is personally reviewed by a qualified accountant who checks your figures, applies relevant allowances, and explains any tax due before submission.
We prepare and file your SA100 and all required schedules, deal directly with HMRC on your behalf, and guide you through balancing payments and deadlines. We also help with late returns, penalty appeals, and past-year corrections.

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Eligibility

Who Needs a Self Assessment Tax Return

You must file a Self Assessment return if you receive income that HMRC hasn’t already taxed. This includes self-employed earnings, rental income, dividends, and foreign income. You’ll also need to file if you’re a company director, a partner in a business, or earn more than £150,000 through PAYE.
Many people also complete a Self Assessment to claim allowances such as pension contributions or Gift Aid donations. If you’re unsure, our accountants can confirm whether you need to register.

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Self Assessment accountant meeting with client reviewing tax documents and explaining HMRC filing process.
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What We Need to Complete Your Return

Before we begin, you’ll need to provide a few key records so we can prepare your Self Assessment accurately. This includes your P60 or P45, details of income and expenses if you’re self-employed, and any rental or investment income.
We’ll also need pension contribution statements, Gift Aid donation records, and details of any capital gains from property, shares, or crypto. You can securely upload everything through our SBX Client Portal powered by TaxDome.

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Our Process

How Our Self Assessment Service Works

We keep the process simple and stress-free. First, we’ll arrange a short call to review your situation and confirm a fixed fee. Once you’ve uploaded your records, our accountants prepare and review your Self Assessment return. You’ll receive a clear summary showing your tax position before we submit it to HMRC.
When filed, we confirm receipt and provide your exact payment figures with due dates, so you always know what to pay and when.

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Self Assessment accountant showing client a tax summary and explaining HMRC payment dates.
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Transparent Fees

Simple Fixed-Fee Pricing

Our Self Assessment service is priced clearly with no hidden extras.
Most individual returns start from £165, which includes full preparation, review, and HMRC online filing.
If your return involves capital gains, crypto transactions, or multiple income sources, we’ll quote upfront before starting work.
You’ll always know your cost in advance, and we confirm all fees in writing before any submission.

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Deadlines

Important Self Assessment Deadlines

The deadlines set by HMRC are strict, and missing them can result in penalties.

  • Paper returns: 31 October 2025
  • Online returns: 31 January 2026
  • Second payment on account (if due): 31 July 2026
    We recommend starting early so you can check figures calmly, plan for any tax due, and avoid last-minute rushes or fines.
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What should you know before filing your Self Assessment?

Before filing your Self Assessment, make sure your income, expenses, and reliefs are correctly recorded. Register early with HMRC to get your UTR, check what tax you owe, and keep proof of all records. Our accountants guide you through every step to ensure full accuracy and compliance.

Talk to SBX about your Self Assessment

Chartered Accountants in London & Slough for Small Businesses

SBX helps you stay compliant & keep more of what you earn with expert tax, accounts, and bookkeeping services.

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