Describe the question the receipt supports
A receipt records a purchase, but it may not explain the business reason or the tax period being reviewed. Add a short note in your own working index identifying the purpose and the related activity. Keep the original intact so an annotation does not become a substitute for the source document.
Flag mixed or incomplete details
If the purchase covers several items or has more than one use, write that complication down. Preserve any supporting record needed to understand the split or context. Do not assume that a business-related label establishes a deduction. The index should make a qualified review easier by showing where classification or further evidence is still required.
Tie the index to the year folder
Use a consistent reference between the receipt, statement entry, and year-specific working summary. Keep the date of the document and the relevant period clear. When preparing a filing or account discussion, explain which questions remain unresolved and what source might answer them. Save the version of the index actually supplied through a confirmed secure channel, rather than relying on later recollection.