Which mistake is most common
Gender pay gap reporting uses two separate calendars: one for the period over which you measure the figures, and one for the period in which you report on them. The most common mistake is that employers confuse the two and think that the measurement period and the reporting date are the same. This leads to figures covering the wrong period, a report that is prepared too late, or a headcount taken at the wrong moment.
The result is usually not that reporting fails entirely, but that it is completed under time pressure with data that is difficult to substantiate afterwards. Anyone who knows in advance which period counts and when that period closes can largely avoid this problem.
Why there are two calendars
The Directive deliberately distinguishes between the moment when the gender pay gap is determined and the moment when that result is disclosed. The measurement period is the period during which remuneration data is collected and compared. The reporting period is the period in which the resulting figures must be submitted or published. Between these two lies a buffer, intended for checking data, reviewing categories and, where necessary, preparing explanations.
This buffer is exactly where things go wrong. Companies see the reporting date as the moment to plan around and forget that the measurement period has already closed. Anyone who only then starts collecting data is in fact measuring a different period than the one they must report on.
How the mistake happens in practice
Three situations come up repeatedly. The first is that a company uses its financial year instead of the period that the Directive designates as the measurement period. This difference seems small, but it has knock-on effects in every category and every figure derived from it.
The second is counting the number of employees. Whether a company falls under the reporting obligation depends on the workforce at a designated moment, not on the day someone checks it. A company that is just below or just above the threshold can make a mistake by using a different reference date than the one that applies.
The third is that the HR department and the finance department each maintain their own calendar. HR works with the personnel year, finance with the tax year, and no one has specified which of the two is authoritative for reporting. By the time this difference comes to light, the measurement period has often already passed.
What that means for how your data is categorized
The two calendars also affect how job classifications are structured. A classification that changes halfway through a measurement period makes comparison between groups harder to substantiate: did a difference arise from an actual remuneration change, or because people were placed in a different category partway through? Anyone who establishes the classification of jobs into equivalent categories before the measurement period begins can largely avoid this question. More on this classification is in the guidance on job classification and equal work.
How to prevent this
In practice, it works best to establish the two calendars separately from each other, with a separate date for closing the measurement period and a separate date for the report itself. Put those two moments in the schedule of both HR and finance, so that no one accidentally lets them overlap with their own financial year.
It is also advisable to determine in advance at what point the workforce is counted, and to do it the same way each year. This creates a fixed, repeatable process instead of an annual sorting-out exercise.
Whether your company is currently subject to the reporting obligation and which period applies to you can be determined with a few questions. In a few questions you can see where you stand now, without needing an account for that. Anyone who wants to know exactly where the terms and thresholds we use come from will find that in the explanation of the sources we use.
Finally
The two calendars are not a side issue, but the foundation of a well-substantiated report. If you clarify them early on, you save yourself trouble later with data that no longer matches. Are you unsure whether your planning aligns with the correct periods? Check the knowledge base or take the free quick scan to see what applies to your company.