A clear, practical guide to who needs to file, what’s involved, the deadlines that recur every year and the figures that matter, and how GCD Global Consultants takes the stress out of getting it right.

1What Exactly Is Self Assessment?

Self Assessment is the system HM Revenue & Customs (HMRC) uses to collect Income Tax, and certain National Insurance, from people whose tax is not fully deducted at source through PAYE. Each year, millions of UK taxpayers report their income, gains, allowances and reliefs on a tax return so that HMRC can calculate exactly what is owed, or repaid.

For most employees, tax is handled automatically through their payslip and no return is needed. But for the self-employed, landlords, company directors, investors and higher earners, Self Assessment is how their tax position is declared and settled.

2Do You Need to File? Find Out

You will usually need to complete a Self Assessment return for a tax year if you were any of the following:

• A sole trader with gross trading income above the £1,000 trading allowance
• A partner in a business partnership
• A company director with income that is not taxed under PAYE
• A landlord with property income above the £1,000 property allowance
• A higher earner caught by the High Income Child Benefit Charge, which applies where income exceeds £60,000 and reaches a full charge at £80,000
• In receipt of untaxed income, dividends, savings interest, foreign income or rental income, above the relevant allowances
• Liable to Capital Gains Tax on the disposal of assets above the annual exempt amount of £3,000
• Claiming certain reliefs or repayments, such as higher-rate pension tax relief or work expenses

If you are unsure whether you fall within Self Assessment, it is always worth checking, registering late can trigger penalties.

3Key Dates You Can’t Miss

The UK tax year runs from 6 April to 5 April. The headline deadlines fall on the same dates every year:

4Getting Started: Registration

First-time filers must register with HMRC to obtain a Unique Taxpayer Reference (UTR) and set up a Government Gateway account, using form SA1, or CWF1 if you are self-employed. Allow time for this, as the UTR is sent by post.

You then gather your records of income and expenses and complete the main return (the SA100), together with any supplementary pages relevant to your circumstances: employment (SA102), self-employment (SA103), UK property (SA105), foreign income (SA106), capital gains (SA108) and residence (SA109).

5Payments on Account Explained

If your Self Assessment bill, Income Tax plus Class 4 National Insurance, is £1,000 or more, and less than 80% of your tax was collected at source, HMRC asks you to make advance payments towards the following year’s bill. Each Payment on Account is 50% of the previous year’s liability, due on 31 January and 31 July.

6National Insurance for the Self-Employed

Self-employed individuals pay Class 4 National Insurance through their Self Assessment return, at 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270.

7The Numbers That Matter

8Miss the Deadline? The Penalties

• A £100 fixed penalty the moment you miss the 31 January online deadline, even if you owe nothing
• After three months: £10 a day, up to a maximum of £900
• After six and twelve months: a further £300, or 5% of the tax due, whichever is higher
• For late payment: interest runs from the due date, with 5% surcharges after 30 days, six months and twelve months

9The Big Change: Making Tax Digital

Under Making Tax Digital for Income Tax (MTD for ITSA), the once-a-year return is being replaced with digital record-keeping and quarterly updates. The rollout is phased by income level:

10Smart Tips to Stay Ahead

• Register early, a UTR can take time to arrive, and late registration can lead to penalties
• Keep good records, the self-employed should retain records for at least five years after the filing deadline
• Claim everything you’re entitled to, allowable expenses, reliefs and allowances are easily overlooked
• Don’t wait for January, filing early avoids the rush and gives certainty over what you owe
• Set money aside, putting funds by through the year softens the January bill

?Your Questions, Answered

This guide is provided for general information only and does not constitute personal tax advice. Tax rules, allowances and thresholds are subject to change. For guidance tailored to your circumstances, please contact us.