How payroll works for small businesses is one of those things that sounds simple until you’re actually doing it. Pay someone a wage, sorted. But the moment PAYE, National Insurance, Real Time Information and pension obligations enter the picture, it gets complicated fast.

What payroll actually involves

At its core, payroll is the process of working out how much each employee is owed, deducting the right amount of tax and National Insurance, and paying them the correct net amount. You also need to work out how much employer’s National Insurance you owe on top. That’s three moving parts before you’ve even thought about pensions or student loan deductions.

The system HMRC uses to collect income tax and National Insurance through employment is called PAYE, which stands for Pay As You Earn. Every time you run payroll, whether that’s weekly, fortnightly or monthly, you need to calculate the deductions against each employee’s tax code and earnings. Get it wrong and employees either underpay tax across the year or take home less than they should.

What HMRC expects from you every pay period

Since 2013, employers have been required to report payroll information to HMRC in real time. This is called Real Time Information, or RTI. It means you can’t just tot everything up at year-end. You submit a Full Payment Submission to HMRC on or before each payday, every single time.

If you miss a submission or submit late, HMRC can and does issue automatic penalties. Keeping up with changing payroll regulations is one of the biggest pain points for small businesses managing payroll themselves, and it’s not hard to see why. The rules around tax codes, statutory payments, and employer obligations shift regularly, and it’s on you to stay current.

What’s changed in payroll rules recently

There’s been a fair amount of movement in payroll obligations heading into the 2026-27 tax year. As mentioned, new National Minimum Wage and National Living Wage rates applied from 1 April 2026. On top of that, the Small Employers’ Relief compensation rate has increased from 8.5% to 9%, which affects how much you can reclaim on statutory payments like Statutory Maternity Pay.

There have also been changes to tax and National Insurance exemptions around reimbursed homeworking equipment, eye tests and flu vaccinations, which apply from 6 April 2026. None of these are huge individually, but taken together they mean your payroll setup from last year may need updating. The legislation underpinning all of this sits in the HMRC Employer Further Guide to PAYE and National Insurance, which is updated each tax year.

When it makes sense to stop doing this yourself

A lot of small business owners start doing payroll themselves. That’s fine when you have one or two employees and a quiet month. The problem is payroll doesn’t stay simple. Statutory sick pay, maternity pay, pension auto-enrolment, mid-month starters, leavers, tax code changes from HMRC mid-year. Each one adds time and risk.

The question isn’t really whether you can do it yourself. It’s whether it’s the best use of your time and whether the cost of a mistake outweighs the cost of handing it over. There are currently 30.3 million payrolled employees across the UK. The vast majority of their employers aren’t processing payroll manually. Outsourcing isn’t a sign your business is small. It’s what real businesses do.