How payroll works is one of those things most small business owners never think about until there’s already someone starting on Monday and a deadline looming on Friday. It’s not complicated once you understand the moving parts, but there are real obligations here and HMRC does notice when they’re missed.

What Payroll Actually Means (and What PAYE Is)

Payroll is the process of paying your employees, calculating the correct tax and National Insurance deductions, and reporting everything to HMRC. The system that makes this work is called PAYE, which stands for Pay As You Earn. It’s the mechanism HMRC uses to collect income tax and National Insurance from employees before the money ever reaches their bank account.

As the employer, you’re responsible for calculating those deductions correctly every single pay period, whether that’s weekly, monthly, or anything in between. You don’t wait until the end of the year to settle up with HMRC. You deduct, report, and pay on time, every time.

What HMRC Expects Every Time You Run Payroll

Before you pay anyone for the first time, you need to register as an employer with HMRC. Once you’re registered, every time you process a pay run you’re required to submit what’s called a Full Payment Submission, or FPS. This is a digital report that tells HMRC exactly who you paid, how much, and what deductions you made. It has to be submitted on or before the day you actually pay your employees.

If no one is being paid in a particular period, you may still need to submit an Employer Payment Summary (EPS) to tell HMRC that. Missing that submission counts the same as missing a payroll submission in HMRC’s eyes. These aren’t optional extras, they’re part of a system called Real Time Information (RTI), and it’s been mandatory for UK employers since 2013.

What Happens If You Miss a Deadline or Get It Wrong

HMRC charges penalties for late Full Payment Submissions, and the amounts are based on how many employees you have. If you have between one and nine employees, the penalty is £100 per late submission. It rises to £200 for ten to forty-nine employees, £300 for fifty to two hundred and forty-nine, and £400 for two hundred and fifty or more. There is an exception if you file within three days of payday, but HMRC can still act if late filing becomes a regular pattern.

There are also changes coming around benefits and expenses. From the 2027 to 2028 tax year, mandatory payrolling of benefits in kind begins, with a grace period on penalties for honest errors. From 2028 to 2029 onwards, full penalties and interest will apply. HMRC is expected to publish draft legislation and guidance in the first half of 2026, so this is worth keeping an eye on if you provide any taxable benefits to your staff.

Should You Run Payroll Yourself or Hand It Over?

If you have one or two employees and you’re comfortable with the software, running payroll yourself is entirely possible. Tools like Xero make the submission process much more straightforward than it used to be. The issue for most small business owners isn’t the technology, it’s the time, the ongoing compliance awareness, and the confidence that it’s been done right.

Where I tend to see things go wrong is when payroll becomes one of those jobs that gets done in a rush at the end of a long week. A late submission here, an incorrect figure there, and suddenly you’ve got a penalty notice and confused employees asking why their payslip looks different. If that pattern sounds familiar, handing payroll to someone who does it every month without fail is usually worth more than it costs.