Vérifié le 21 septembre 2026 — art. 27 LIFD, art. 957, 957a et 958f CO, barèmes AVS/AI/APG au 1er janvier 2026, plafonds du pilier 3a 2026.
The law fits in one sentence. Everything else — the car, the home office, meals, the phone — is a matter of proof, and proof is built during the year, not when you file your return.
The rule, in one sentence
Article 27(1) of the Federal Direct Tax Act states: taxpayers engaged in self-employed gainful activity may deduct “expenses justified by business or professional use”.
There is no closed list. There is no federal flat-rate scale for the self-employed as there is for employees. There is one criterion, and it is up to you to show that an expense meets it.
This is the most misunderstood consequence of the status: the tax authority does not have to prove that an expense is private. You have to prove that it is business-related. An expense you cannot link to a service, a client or a work tool will be added back — all the more easily if it is a comfortable one.
What the law names explicitly
Paragraph 2 of article 27 lists what is “in particular” part of justified expenses:
- depreciation and provisions within the meaning of articles 28 and 29 DFTA;
- actual losses on business assets, provided they have been recorded in the books ;
- contributions to pension institutions for the company’s staff, provided any use contrary to their purpose is excluded;
- interest on business debts;
- training and continuing education costs for staff for professional purposes, including retraining;
- profit-skimming sanctions, insofar as they are not penal in nature.
The condition slipped into the second item applies to everything else: an expense that is not recorded in the books does not exist for tax purposes. This is where most legitimate deductions are lost.
What the law explicitly excludes
Paragraph 3 is short and unambiguous. The following are not deductible:
- bribes within the meaning of Swiss criminal law;
- expenses that enable offences to be committed or that are the consideration for committing offences;
- fines and monetary penalties ;
- administrative financial sanctions, insofar as they are penal in nature.
A parking fine picked up while visiting a client is therefore not deductible, even though the trip was. The distinction is not moral, it is legal: lawmakers wanted the penalty to be borne by the person who earned it.
Where it really matters
In practice, add-backs almost always concern the same six items, and always for the same reason: the private share.
The car
It is the item most often adjusted. Without a logbook, the tax authority applies a flat private share and sets it in its own favour. A logbook kept to the kilometre — date, route, purpose, client — takes ten minutes a week and is often worth several thousand francs in an audit.
The home office
Deductible if the room is dedicated to the business and you have no other premises available. The share is calculated on floor area, not on impressions. A table in the living room is not an office; a converted bedroom is.
Meals
A meal eaten alone is a living expense: private. A business meal is deductible, but it must be documented — the guest’s name and the purpose of the meeting noted on the back of the receipt are enough, and nothing replaces them two years later.
Phone and internet
Rarely accepted at one hundred percent when there is a single subscription. Two separate subscriptions settle the question once and for all and cost less than an argument with a tax assessor.
Clothing
Deductible only if they cannot be worn outside work: safety gear, work coat, branded uniform. A suit is still a suit, however many meetings you have.
Training
The law expressly refers to training of staff. For the self-employed person, training that maintains or develops the existing business is an expense; training that opens up a new activity follows a different logic and is open to discussion.
Social security contributions, a special case
Your personal AHV, IV and EO contributions are deductible from taxable income. The compensation fund knows this, which is why it adds them back to the net income reported by the tax authority before recalculating: “personal AHV, IV and EO contributions already paid are added back to net income according to the tax assessment”.
As at 1st January 2026, the full rate is 10.0% — 8.1% AHV, 1.4% IV, 0.5% EO — plus the fund’s administrative costs. Below CHF 60,500 of annual income a sliding scale applies, and below CHF 10,100 the minimum contribution is CHF 530 per year.
The fund also deducts from the relevant income an interest on the equity invested in the business. This deduction does not need to be claimed: it simply requires the equity to be shown correctly on the balance sheet.
On the pension side, a self-employed person without a pension fund can pay into pillar 3a 20% of net business income, up to CHF 36,288 in 2026. With a pension fund, the ceiling drops to CHF 7,258. It is by far the most profitable deduction available to the self-employed — and the most often under-used.
Bookkeeping decides the deduction
All of the above assumes bookkeeping. The Code of Obligations sets the threshold in article 957: above CHF 500,000 of turnover in the last financial year, a sole proprietorship keeps full accounts and presents financial statements. Below it, it only keeps “accounts of income and expenditure and of assets”.
“Only keeps” is misleading. Paragraph 3 specifies that the principle of proper bookkeeping applies by analogy, and article 957a defines it: complete, accurate and systematic recording, each entry supported by a voucher, clarity, traceability. Simplified bookkeeping is still bookkeeping.
Finally, article 958f requires books and vouchers to be kept for ten years, starting from the end of the financial year. Electronic storage is accepted provided the link to the transactions is guaranteed and the records remain readable at all times — which rules out the hard drive of a computer replaced in the meantime.
That is why we insist so much on continuous recording rather than a binder caught up in March. An expense recorded when it arises, with its voucher, is defensible. The same expense reconstructed eleven months later is an expense to negotiate.
Before you decide, let's talk about your situation
Thirty minutes by video call, free and without obligation.
Choose a slot