A sole proprietorship has no separate corporate tax: your business profit flows straight into your personal tax return. Which also means the quality of your tax return isn't decided in March — it's decided all year long in your bookkeeping. Book as you go and year-end takes two relaxed hours. Collect receipts in a box and it takes two stressful weekends.
Bookkeeping is half the tax return
Alongside the main tax form, self-employed filers need an annex with their business result — and behind it, a statement: below CHF 500,000 in annual revenue a simplified income-expense statement is enough (the Swiss «Milchbüechli», art. 957 para. 2 CO); above that, a full balance sheet and income statement are required. Three things decide whether that statement holds up with the tax office:
- Complete receipts: The burden of proof for deductions is on you. No receipt, no deduction — keep invoices and receipts for 10 years.
- Accrual timing: What counts is when the work was performed — not when the money arrived. A December job belongs in the old year, even if the invoice is paid in January.
- Clean separation of private and business: Car, phone, home office — mixed use requires a private-use share, or the tax office will add it back for you.
What a bookkeeping tool like einzly takes off your plate
Exactly this legwork can largely be automated today. We work with einzly — a Swiss bookkeeping tool built for sole proprietors and freelancers with no accounting background:
- QR invoices created and sent, including automatic payment reminders
- AI-assisted bookkeeping: capture receipts, match payments, assign categories
- VAT returns prepared automatically if you are VAT-registered
- Annual statement at the push of a button — income-expense statement or P&L, ready for the tax return
The point isn't any single feature — it's the effect: your statement is done at year-end instead of something you have to reconstruct.
Where bookkeeping ends — and tax optimisation begins
A clean statement shows what happened. The tax return decides what you make of it. For sole proprietors, the big levers sit outside the bookkeeping:
- Pillar 3a: Without a pension fund you may pay in 20% of your net earned income — up to CHF 36,288 per year. The pillar 3a calculator shows what that saves in your municipality, including retroactive buy-ins since 2025.
- Pension fund buy-ins: If you join a pension fund, voluntary buy-ins add another tax lever — plannable over several years.
- Private-use shares and depreciation: There is room and there are limits (the federal tax administration publishes guide values and maximum rates). Too aggressive gets added back; too cautious gives money away — the right line depends on your case.
These decisions play out over several years — which is why they belong in a plan, not in a last-minute filing session.
The workflow that works
- During the year: capture invoices, receipts and payments in einzly as you go — a few minutes per week.
- In January: generate the annual statement at the push of a button and sanity-check it.
- Then: the tax return — yourself with the cantonal forms, or handed over: at FIN your einzly statement flows directly into the tax return via an interface, and we review the optimisation levers for next year at the same time.
That keeps bookkeeping a minutes-per-week side job — and turns the tax return from an obligation into an optimisation appointment. Want to see how this looks for your business? Here's the full workflow — or book a free intro call.