R&D additional information form
R&D additional information form: what to prepare
HMRC requires additional information for R&D claims. Preparing it early usually improves both the claim and the internal review.
Start with the R&D tax credit calculator if you need a quick claim-value estimate before reading the detail.
Project evidence
The form pushes claimants to explain the advance sought, the uncertainties faced, and the work done to resolve them. Generic product descriptions are usually not enough.
Cost evidence
Payroll, subcontractor, externally provided worker, software, consumable, and data/cloud costs should be traceable to the qualifying work and accounting period.
Why it affects the calculator
The calculator starts with your input spend. The AIF process often changes that spend because it forces a more precise link between costs and qualifying activities.
Important note
R&D tax relief depends on scheme rules, company facts, accounting periods, and HMRC evidence standards. Treat this page as research support, not tax advice.