In your R&D claim, you need to provide a reasonable explanation for how much time your staff worked on R&D claims. Staff costs come under 2 categories of activities that directly contribute to the resolution of technological uncertainty and qualifying indirect activities. This is because staff costs are a qualifying expenditure. The best way to present this information to HMRC is through timesheets. Because many businesses retrospectively claim for R&D tax credits, they’re naturally not keeping documentation because they’re not aware of either RDEC or the SME R&D tax credit scheme.