When the Payroll Stops Short: Reporting Extra Income Alongside a Job in 2026/27

PAYE is an efficient way to collect tax on a salary, but it is not a complete tax settlement for every employee. A growing number of people earn additional income from freelance work, online selling or hiring out equipment. Those receipts may sit outside the payroll, and HMRC will not usually know about them unless the taxpayer discloses them or a third party reports them.

The practical risk is not only an adjustment to a tax code. It is the possibility of an unexpected Self Assessment liability, a late-registration penalty or a January cash-flow problem. A side income of a few thousand pounds can feel modest month by month, but once it is added to salary and taxed at the employee’s marginal rate, the bill can be material.

Why PAYE only sees the main job

An employer operates PAYE using the tax code issued by HMRC. That code reflects the information HMRC holds at the time, usually the main employment, any taxable benefits and perhaps a small amount of untaxed income. It does not automatically reflect new freelance receipts, marketplace sales or rental income from equipment.

A tax code is therefore a collection mechanism, not a disclosure system. HMRC may later adjust the code to collect tax on some untaxed income, but that does not remove the taxpayer’s obligation to register for Self Assessment or file a return where the rules require it. Employees should treat a coding notice as something to check, not as confirmation that the side income has been properly reported.

When a second stream becomes reportable

The first question is the nature of the income. Freelance work, consultancy, gig work and regular online selling are usually trading income. Hiring out equipment or other property is more likely to be property income. Selling personal possessions occasionally is generally not taxable, but frequency, organisation and a clear profit motive can turn an activity into a trade.

For 2026/27, a sole trader whose gross trading income exceeds £1,000 will generally need to tell HMRC and file a Self Assessment return. The same broad principle applies to property income above the £1,000 property allowance, subject to specific exclusions such as rent-a-room relief. If the gross receipts are at or below £1,000, the relevant allowance may mean no return is required solely because of that income, but records should still be kept.

If a taxpayer already files Self Assessment for another reason, the side income should be brought into the return. The allowances may then reduce the taxable amount, but they do not make the income invisible.

The £1,000 allowances are not a tax-free bonus

The trading allowance and the property allowance each provide up to £1,000 of relief. They are useful, but they are not cumulative in the way some people assume. For trading income, a taxpayer can deduct the £1,000 allowance instead of deductible expenses. The same choice applies to property income, although the property allowance does not fit every property stream.

The allowance cannot be used alongside actual expenses for the same income. If allowable expenses are higher than £1,000, normal accounts will usually produce the better result. If expenses are lower, the allowance may be simpler. The allowance cannot create a loss, and it does not reduce the gross figure for VAT purposes or for deciding whether a registration threshold has been crossed.

A common error is to treat the £1,000 as an extra tax-free band. It is not. It is a deduction from gross income, and only where the conditions are met.

How HMRC uses tax codes after disclosure

Once HMRC knows about untaxed income, it may collect the tax through an adjusted PAYE code where the amount is suitable for that approach. This can be convenient, but it can also create confusion if the side income varies or if the taxpayer later registers for Self Assessment.

Where Self Assessment is required, the return remains the primary document. A code adjustment may collect payments on account or tax for an earlier year, but it does not replace the return. Employees should read coding notices carefully, compare them with their records and correct anything that looks inconsistent. A code that collects too little can store up a future bill; a code that collects too much can put pressure on monthly cash flow.

Records to keep from the first receipt

Good records are the difference between a straightforward return and a stressful reconstruction. A separate bank account for side income is helpful but not essential. What matters is a clear record of gross receipts, platform fees, expenses and the purpose of each cost.

Useful evidence includes marketplace statements, invoices, payment processor reports, mileage logs and receipts. Where equipment is hired out, keep the hire agreements and a schedule of income and related costs. Where a room or home workspace is used, retain a reasonable basis for any claim. For 2026/27, individuals should generally keep Self Assessment records for five years after the 31 January filing deadline, so this is not a short-term habit.

The January liability and payments on account

A side income can turn a modest tax position into a payments-on-account case. If the tax due through Self Assessment is more than £1,000 and less than 80% has been collected at source, HMRC will usually require payments on account towards the following year. That means the January filing date can bring a larger bill than the taxpayer expects, with a further payment due in July.

For 2026/27, the online filing deadline is 31 January 2028. Registration for Self Assessment is generally required by 5 October 2027 where a new source needs to be reported. Missing those dates can lead to penalties and interest, so the time to check the position is during the tax year, not after it has ended.

A practical review for employees

Start by listing each income stream and its gross receipts for 2026/27. Decide whether it is trading, property or a private sale. Compare the £1,000 allowance with actual expenses. Check whether registration is needed by 5 October 2027. Keep platform statements and bank records together. Review any coding notice from HMRC. Finally, set aside a realistic proportion of the profit for tax rather than waiting for the January statement.

PAYE will continue to handle the salary, but it will not manage a second income by default. A short review now is preferable to discovering in January that the payroll was only ever part of the picture.