Self Assessment basics and basis periods
Why your first tax bill covers a period you do not recognise, how the cash basis differs from accruals, what SA302 adjustment income means, and why HMRC's figures sometimes differ from your own. These guides cover the mechanics of the return itself.
10 guides in this topic.
Cash Basis & MTD ITSA: Invoice Date vs Payment Date Explained
Under Making Tax Digital for Income Tax Self Assessment, cash basis sole traders must record income when money actually lands in their account — not when they raise an invoice. Getting this wrong could mean misreporting quarterly figures to HMRC. Here's exactly what you need to know.
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Basis Periods for New Sole Traders: Your First Tax Bill Explained
Starting out as a sole trader means navigating HMRC's rules on basis periods — the time frame used to calculate which profits are taxed and when. Under the new tax year basis rules that took full effect from 2024/25, things work differently to how they did before. Here is exactly what you need to know about your first year's tax bill.
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Cash Basis vs Accruals: When Does a Late Invoice Count as Income?
If a client pays your invoice three months late, do you declare that income in the tax year you raised the invoice or the year you received the money? The answer depends on which accounting method you use — and getting it wrong can land you with an unexpected tax bill. Here is exactly how the rules work for sole traders and freelancers under Self Assessment.
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Why Your First Tax Returns Don't Match Your Accounting Year
If you've just started out as a sole trader, your first few Self Assessment returns can look confusing — the income on your tax return often doesn't match your accounting year. This is down to HMRC's basis period rules, which were overhauled in 2024 but still affect how your early years are calculated. Here's what you need to know.
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SA302 Adjustment Income: Why HMRC's Figures Differ From Yours
If your SA302 shows a different income figure to what you submitted on your Self Assessment return, you're not alone. HMRC applies adjustments that can catch freelancers and sole traders off guard. Here's what adjustment income means, why it appears, and exactly how to challenge it.
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Cash Basis Accounting: Save Tax and Switch on Self Assessment
Cash basis accounting lets sole traders and freelancers pay tax only on money they've actually received, not invoices they're still waiting on. It can reduce your tax bill, simplify your bookkeeping, and ease your cash flow. Here's exactly how it works and how to switch.
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How to Correct Past Self Assessment Returns: A Practical Guide
Made a mistake on a previous Self Assessment return? You have options, but time limits matter. This guide explains how to amend returns, what happens when HMRC finds errors first, and how to protect yourself from unexpected tax bills.
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How to Correct Old Self Assessment Returns Before HMRC Acts
Made a mistake on a previous Self Assessment return? You have a limited window to put things right before HMRC comes to you. This guide explains exactly how to amend old tax years, what deadlines apply, and how to reduce your risk of investigation.
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Allowable Expenses UK Freelancers Miss on Their Self Assessment
Many UK freelancers leave money on the table every year by overlooking legitimate allowable expenses on their Self Assessment return. From home office costs to professional subscriptions, these missed deductions can add up to hundreds of pounds in unnecessary tax. Here is what to claim before you file.
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Allowable Expenses UK Freelancers Forget on Their Self Assessment
Missing legitimate allowable expenses means paying more tax than you owe. From home office costs to professional subscriptions, many UK freelancers consistently overlook deductions that HMRC fully permits. Here are the most commonly missed expenses and how to claim them correctly.
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