Monthly obligations
Every registered employer in the UK carries the same core monthly obligation, submit an RTI declaration and pay over PAYE, National Insurance and the Apprenticeship Levy by the seventh of the month following the one in which employees were paid. Missing that date, even by a day, can trigger penalties and interest from HMRC, so the RTI process deserves to be treated as a fixed monthly deadline rather than something squeezed in whenever there is time. Getting the numbers right depends on accurate payroll calculations in the first place, which is where most of the actual risk sits, a payroll run with an incorrect PAYE calculation does not just cost money to fix, it also means your RTI was wrong the moment you filed it.
Bi annual reconciliation
Twice a year, employers must complete an year end reconciliation, matching what was declared and paid across RTIs against the actual tax certificates, P60s and IT3as, issued to employees. The interim reconciliation covers the first half of the tax year and is typically due in October, while the annual reconciliation covers the full tax year and falls in May. This is the point where small discrepancies from earlier in the year surface, an employee who was under or over deducted, a benefit that was not correctly taxed, or a leave payout that slipped through incorrectly categorised. Businesses that reconcile informally each month tend to sail through year end season, while those that only look at the numbers twice a year often find themselves untangling months of small errors under time pressure.
Employee tax certificates and National Insurance
P60 and IT3a certificates need to be accurate and issued on time as part of the annual reconciliation, since employees rely on them to file their own personal tax returns. Separately, National Insurance contributions need to be declared not only to HMRC but also to the Department of Employment and Labour through the National Insurance system, which is a step that catches out employers who assume the HMRC submission covers everything. the Apprenticeship Levy obligations follow a similar pattern of needing to be calculated correctly every pay period rather than adjusted after the fact.
How payroll software helps
The realistic way most UK employers stay on top of all of this is by using payroll software that has the compliance rules built in rather than tracking legislation changes manually. A good system calculates PAYE, National Insurance and the Apprenticeship Levy correctly at the point of each pay run, keeps RTI figures accurate as you go so bi annual reconciliation is a formality rather than a scramble, and generates P60s and IT3as without manual formula work. The businesses that struggle most with compliance are usually the ones still running payroll through spreadsheets, where a single formula error can quietly compound across an entire tax year before anyone notices. Whether you choose a full featured platform built for multi country compliance or a simpler tool focused purely on UK payroll, the return on investment tends to show up the first time a reconciliation goes smoothly instead of turning into a week of detective work.
