Every legitimate expense you record cuts your taxable profit — and for CIS subcontractors it usually grows the refund. Yet most self-employed people leave money on the table simply because the receipt never made it home. Here's what counts, and how to stop losing it.

The golden rule

An expense is allowable when it's incurred wholly and exclusively for the business. Mixed-use costs (your phone, your van, your home) can be claimed for the business proportion — a defensible split, applied consistently.

The big categories

  • Materials and consumables bought for jobs — from timber to toner.
  • Tools and equipment — purchase, repair and replacement.
  • Vehicle costs — actual running costs or mileage at HMRC's approved rates, not both.
  • Insurance — public liability, tools cover, professional indemnity.
  • Phone, software and subscriptions (business proportion).
  • Training that updates existing skills, plus certification and card renewals.
  • Accountancy fees and bookkeeping software — yes, they're allowable.
  • Use of home — simplified flat rate or a calculated share of household costs.

The commonly missed ones

Parking (not fines), tolls and congestion charges. Small cash purchases — the £6 fixings, the £4 blade. Waste disposal. PPE and workwear with a logo or protective function (ordinary everyday clothing doesn't count). Bank charges on a business account. Each is small; a year of them isn't.

What you can't claim

Ordinary clothes, your normal commute, client entertaining, personal spending mixed into the business account (record it as personal — SubReady tracks drawings separately), and fines or penalties. When in doubt, record it anyway with a note — your accountant can decide, which beats forgetting it existed.

This article is general information for UK sole traders and subcontractors, not tax, accounting or financial advice. Rules change — check current HMRC guidance or speak to an accountant about your own position.