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Article by GoSimpleTax

Once upon a time, not too long ago, most people would have had one income source – usually their job, working for one employer, But, over time, things have changed. Many people now have more than one income source, either through choice or necessity.

Lots of people with jobs also have a nice side-hustle or perhaps earn additional cash from renting out property, whether in the UK or overseas. Many expat Brits still earn income that’s taxable in the UK, whether from property, employment or UK business interests. 

Sources of taxable income can include employment, self-employment (including subcontractor payments under the Construction Industry Scheme), rental income or income from share dividends, pensions, savings interest or capital gains (which can be payable after selling certain assets that have increased in value).

Reporting Multiple Income Sources to HMRC

Taxable income must be reported each tax year to HMRC via Self Assessment, the system the UK tax authority uses to collect Income Tax from a wide variety of sources. Once registered for Self Assessment, a taxpayer must complete an annual Self Assessment tax return (the SA100), which is eight pages long.

The SA100 is the main part of the Self Assessment tax return and you use it to report income from employment, pensions, savings and dividends. To report taxable income and claim tax expenses for other specific sources, you must also file supplementary pages. These are two pages long and have their own name and number as follows:

• Employment (SA102)
• Self-employment (SA103S or SA103F)
• Business partnerships (SA104S or SA104F)
• UK property income (SA105)
• Foreign income or gains (SA106)
• Capital gains (SA108)
• Non-UK residents or dual residents (SA109)
• A full list of supplementary pages is available on GOV.UK.

Completing all necessary sections of your tax return and relevant supplementary pages ensures that each source of income is taxed correctly and that you can claim available tax expenses. To avoid a late-filing penalty you must file your Self assessment tax return online before midnight on 31 January following the end of the tax year (5 April) during which you earned taxable income. HMRC takes into account all of your taxable income to calculate your overall tax bill, which is determined by the Income Tax Band into which your income falls.

• You’ll pay 20% (basic rate) Income Tax on £12,571-£50,270; 40% (higher rate) on £50,271-£125,140; and 45% (additional rate) on total taxable income above £125,140 (bands are rates are different in Scotland, 2025/26 for all figures).

Need to know! Not accurately reporting all income sources to HMRC can lead to penalties. Falsely claiming tax expenses, deliberate underreporting or failing to report large amounts of taxable income can lead to huge fines. 

Five common mistakes to avoid

Taxpayers with multiple income streams often make the following errors:

• Failing to include all taxable income. For example, not reporting income from employment as well as self-employment income or not reporting taxable side-hustle income. This can happen for innocent reasons, when people do not know that an income source is taxable.

• Not releasing that UK tax can still be payable when you’re an expat who is not resident for UK tax, for example, if you earn income from renting out UK property.

• Entering net instead of gross figures into tax returns. You must always report income before expenses are deducted.

• Not claiming for all allowable expenses (ie costs that HMRC allows you to claim back), which means you pay too much tax. This is particularly common for self-employed and property income.

• Overlooking side hustles, including income from online sales, freelance work or part-time jobs, which must still be reported if taxable. The trading allowance only allows you to earn £1,000 tax-free, anything more can be subject to tax.

Top Tips For Managing Multiple Income Sources

• Maintain digital records throughout the year. It will save you from having to scramble to collect everything shortly before the tax return filing deadline.

• Use accounting software to carefully and conveniently record all of your taxable income and tax expenses.

• Connect your accounting software to your card and bank accounts. It will automates transaction data, saving you lots of time and reducing manual entry errors.

• Keep supporting documents (eg P60s, CIS statements, income-related invoices and sales receipts, dividend vouchers, etc) and store them safely in order.

About GoSimpleTax

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