Distinction from Statutory Working Time Records
Statutory working time records are required under UK employment law (specifically the Working Time Regulations 1998 / WTR 1998 and relevant European case law such as ECJ C-55/18 CCOO): They evidence daily start times, finish times, daily and weekly rest periods, and the 48-hour average weekly limit to regulatory bodies (such as the Health and Safety Executive).
By contrast, a proof of activity (or detailed client timesheet) serves commercial and billing purposes: It demonstrates directly to the client precisely what work was delivered. While both types of record may originate from the same underlying time tracking system, they serve distinct stakeholders and have different mandatory requirements.
Mandatory Information
For a proof of activity to serve as a robust commercial document, it should include:
- Client name, project or contract reference, and the relevant billing period
- Per line item: Date, individual delivering the service, exact duration, and a clear description of the tasks undertaken
- Total hours logged, categorised by service type, fee earner tier, or agreed hourly rate
- Formal sign-off, client approval workflow, or signature block
The specificity of the task description is critical for audit readiness and client transparency. Generic entries such as "Project work" or "Admin" are vulnerable to dispute; precise descriptions such as "Drafted API interface specifications and held alignment meeting with logistics team" are clear, verifiable, and enforceable.
Grant-Funded Projects & R&D Tax Relief
Compliance requirements increase substantially for publicly funded projects, Innovate UK grants, and HMRC Research and Development (R&D) Tax Relief schemes. HMRC and funding bodies demand contemporaneous, person-specific time records with an explicit, unambiguous nexus to eligible qualifying activities. Reconstructed timesheets created retrospectively or broad percentage-based estimates are routinely scrutinised, challenged, and disallowed during compliance checks and HMRC R&D enquiries.
Record-Keeping & Statutory Retention
As the primary supporting voucher for commercial invoicing, a proof of activity forms an integral part of a company's financial and tax records. Under the Companies Act 2006, the VAT Act 1994, and HMRC compliance rules, commercial vouchers and supporting accounting records must be retained for at least 6 years from the end of the relevant financial or accounting period. Furthermore, where timesheets intersect with national minimum wage verification under the National Minimum Wage Act 1998, records must also be maintained for a statutory minimum of 6 years.
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