Allowable vs disallowable expenses in QuickBooks Online: the SA103F mapping
A UK Self Assessment question keeps tripping QuickBooks Online users: which expenses are allowable, which are not, and which box each belongs in.
Self Assessment season brings a recurring question from UK users of QuickBooks Online: which expenses can a sole trader deduct, and which box of the SA103F return should carry each one? We reviewed the formally accepted answer. It comes from Intuit’s own support material, and it rests on one legal test, a short list of barred categories, and a box-by-box mapping onto the software’s account types.
The symptom is quiet but real. Books that look complete produce a taxable profit that no longer matches them, and the return boxes fill with guesswork. The cause is almost always categorisation rather than arithmetic, which is exactly what the accepted guidance addresses.
What does allowable actually mean?
Allowable expenses are costs incurred wholly and exclusively for the business. You deduct them from turnover to arrive at taxable profit, and a lower profit means a smaller Income Tax bill. The boundary is strict. Costs related to personal use cannot appear in the claim at all.
Disallowable expenses are the mirror image. They cannot be subtracted from turnover. Some fail because they are personal, such as everyday living costs. Others fail because the tax authority bars the whole category, and client entertainment is the example the guidance singles out.
Which categories never qualify?
The barred list is short but sharp. Goods or materials used for private purposes are out, and so is depreciation of equipment. Anything you pay yourself is out too: your own salary, drawings, personal pension contributions, and your National Insurance. Payments to staff for non-business work also fail.
Depreciation needs a note. It is disallowed here because equipment is relieved through capital allowances instead, in the section of the return the guidance links to Box 29.
How do the SA103F boxes line up with QuickBooks accounts?
At the core of the accepted answer is a mapping between the numbered boxes on the self-employment pages and the detail types QuickBooks Online uses for expense accounts. Four boxes are set out in full. We summarise them here with the account types alongside.
Box 17, goods for resale or goods used, lines up with Cost of Sales, Supplies and Materials, and Shipping, Freight and Delivery accounts. Raw materials, goods bought for resale, direct production costs, and opening and closing stock adjustments all qualify. Fuel counts only for haulage, taxi, and minicab businesses. Private use of stock and depreciation are barred.
Box 18 holds payments to subcontractors under the Construction Industry Scheme, matched to the Cost of Labour (CIS) detail type. The claim is the full amount paid, before any deductions. The box is reserved for CIS payments, and other costs belong elsewhere on the return.
Box 19, wages, salaries, and other staff costs, maps to Payroll Expenses and Cost of Labour. Salaries, wages, bonuses, employer pension contributions, employer National Insurance, agency fees, and non-CIS subcontractor labour all qualify. Your own pay and pension do not qualify, and neither do staff payments for non-business work.
Box 20, car, van, and travel expenses, is matched to the motor vehicle expense account type. Vehicle running costs and travel spending belong together here rather than scattered across general expense accounts.
The guidance adds one tip worth repeating. Money you take from the business for yourself is drawings, not an expense, and it never belongs in the staff-cost boxes. Track it separately from day one.
Where do the traps bite?
The traps sit where the software is most flexible. Drawings recorded against a wage account will distort Box 19 unless you separate them. CIS payments folded into general labour costs blur the line between Boxes 18 and 19. Depreciation left in an ordinary expense account claims relief the return later reverses.
Client entertainment is the classic surprise. It feels like a business cost, you have the receipt, and the category is still barred outright. Stock drawn for personal use carries the same sting inside Box 17, since only the business share of goods belongs in the cost of sales.
The practical fix
The accepted route is to let the account structure carry the work. Where expense accounts use the detail types the guidance names, the return boxes follow with little manual effort. Mixed costs should be resolved before categorisation, so the personal portion never reaches a deductible box. Drawings, depreciation, and client entertainment stay out of the claim from the start.
None of this is exotic accounting. It is a vocabulary problem, and the accepted answer supplies the vocabulary: one test, a few barred categories, and a clean map from boxes to accounts. Set that map up once, and the question stops recurring.