1. Late RTI submissions
The Full Payment Submission has to reach HMRC on or before payday. One late one per tax year is forgiven. After that it's £100 to £400 a time depending on headcount.
2. Wrong tax codes on starters
A new employee without a P45 needs a Starter Checklist. Defaulting everyone to BR or 0T under-deducts tax, and when HMRC notices, it's the employer who's liable.
3. Not claiming the Employment Allowance
Up to £5,000 off your employer NIC bill, but only if you claim it. A surprising number of small employers we take on have never claimed it at all. We backdate where the rules allow.
4. Directors on the wrong NIC basis
Directors default to the annual NIC basis, but plenty of payroll setups treat them like standard employees. The result is months of wrong deductions and a year-end correction nobody enjoys.
5. Forgetting the P11D
Company cars, private medical, fuel cards. All reportable benefits. Miss the 6 July deadline and the fine starts at £100 per 50 employees per month.
What good looks like
Payroll run weekly or monthly, RTI filed the same day, P32 reconciled, staff paid on time, HMRC paid by the 22nd. Boring. Boring is the goal.