HMRC Box-Number Cheat Sheet — SA103S, SA103F & SA105

Stuck on which HMRC box a cost belongs in when filling in Self Assessment, or just tidying up your bookkeeping? This quick-reference lays out every box on the three most-used pages — SA103S, SA103F and SA105 — in plain English, then settles the ones people get wrong most often.

Inside you'll find:

• The full SA103S self-employment (short) form, box by box
• The complete SA103F, including the disallowable-expenses column
• Every SA105 UK property box, including Rent a Room and the Section 24 finance-cost boxes
• A lookup table mapping 20+ everyday costs (stock, mileage, phone, postage, platform fees, use of home) to the correct box
• The four classic ambiguities settled: postage paid vs charged, use-of-home flat rate vs actual, mileage vs actual vehicle costs, and why mortgage interest isn't an expense

Every box number was read directly off HMRC's current published forms rather than from memory, and a full fact-check with sources is included in the download.

This is a reference and record-keeping aid, not tax advice and not filing software — it tells you which box a figure goes in; the shop's tracker spreadsheets do the adding-up. Two print-ready PDFs are included, A4 and US Letter, seven pages each.