Deductible Expenses for the Self-Employed: What the Tax Office Accepts (and What Gets You Reassessed)

One of the most common areas tax inspectors focus on for self-employed workers (autónomos) is the deductibility of expenses. Spain’s personal income tax rules allow deductions for anything necessary to generate income from the business activity, but the Tax Agency requires the expense to meet three conditions that rarely fail in isolation: it must be linked to the economic activity, properly documented with a full invoice, and recorded in the self-employed worker’s accounting books or registers. When any one of these three pillars is shaky, the expense usually ends up reassessed, with a penalty attached if the Agency finds a lack of diligence.

The exclusive-use test: the key to everything

Exclusive use is the criterion that causes the most headaches. An asset or expense is considered “in use for the business” when it’s used solely and exclusively for the economic activity, with no simultaneous personal use. For items like an office computer or work materials, this is usually easy to prove. The problem arises with mixed-use assets, where the Tax Agency — barring exceptions set out by law, such as certain commercial vehicles — does not allow partial deductibility under personal income tax: either it’s 100% business use, or it isn’t deductible for income tax purposes at all (unlike VAT, where a pro-rata split is allowed, with a 50% presumption for passenger vehicles unless proven otherwise). Keeping the invoice isn’t enough: you need to be able to document the actual business use — visit logs, contracts, client correspondence, mileage records — because in the event of an audit, the burden of proof falls on the taxpayer.

Home-office utilities and vehicles: the hot spots

Since the reform that introduced a specific regime for remote work, self-employed workers who carry out their activity, wholly or partly, from their primary residence can deduct utility costs (water, electricity, gas, phone, internet) by applying a percentage based on the square meters of the home declared as used for business, and then a further reduced percentage to reflect that the home isn’t used for work 24 hours a day. It’s essential to have notified the Tax Agency of which part of the home is used for business (via the corresponding census filing) and to keep utility invoices in the taxpayer’s own name. Recent rulings from the economic-administrative courts have stressed that the percentage applied must be reasonable and consistent with the actual floor space used for business, and that the Tax Agency can require that proportion to be backed up with floor plans, a lease, or a deed.

The vehicle is, by far, the item that triggers the most reassessments. To be deductible for income tax purposes, the self-employed worker must prove exclusive business use — the classic cases being sales agents, hauliers, taxi drivers, or professionals whose activity itself involves travel (couriers, sales reps with a widely spread client base). Outside those profiles, the Tax Agency presumes personal use and disallows the deduction for the vehicle, fuel, insurance, and depreciation, unless there’s solid evidence to the contrary. The practical advice is not to force this deduction if the activity doesn’t clearly justify it, since it’s usually the first thing an inspector checks.

Per diems: how much you can deduct, and how not to lose them

Meal allowances for the self-employed worker themselves are deductible when several conditions are all met: the expense must be incurred at restaurants or catering establishments, paid electronically (card or transfer — cash doesn’t count), tied to travel outside the municipality of the worker’s usual place of business and home address, and within the daily monetary limits set by law (the same limits that apply to employees, varying by whether there’s an overnight stay and whether the trip is domestic or international). Exceeding those daily limits doesn’t invalidate the whole expense, but the excess stops being deductible. The most common mistake is trying to deduct working meals in one’s own home city without any actual travel involved — here the Tax Agency draws a clear line between a per diem (travel-related) and client entertainment expenses, which have their own limits and shouldn’t be confused with the worker’s own meal allowance.

At Zythos Business, we work with self-employed clients and small businesses every quarter on exactly this terrain: reviewing which expenses qualify, how to document them, and what’s better left out before an inspector decides for you. That preventive approach, applied invoice by invoice and tailored to each business, is what prevents nasty surprises in an audit — and what turns tax compliance into a management tool rather than a source of them.