Turnover is not the income figure
For a self-employed person without occupational pension membership, an ordinary 3a contribution is limited to 20% of eligible earned income, subject to the annual ceiling. FTA Circular 18a says self-employed income means the result after tax adjustments and personal OASI, disability and income-compensation contributions, without deducting contributions to recognised pension arrangements. It rules out a deduction when the activity makes a loss. Strong sales do not by themselves justify a 3a payment.
When profit changes between estimates
Suppose a designer has no other activity and no occupational pension membership. In September they forecast CHF 20,000 of eligible income and plan CHF 4,000 in contributions. After the accounts are adjusted, the relevant result is negative: the forecast no longer supports that payment. If confirmed income were CHF 5,000 instead, the percentage calculation would give CHF 1,000 before checking other conditions. These are examples, not universal limits for self-employed workers.
A loss is different from a cash shortfall
An unpaid invoice or a significant purchase can affect cash flow and accounting profit in different ways. Ask your accountant or tax authority which income figure will be used for your return. If you also earn a salary, belong to a pension fund or run another business, get the whole position reviewed: the example does not cover those cases. Money leaving your current account does not prove the contribution qualifies.
What to do before or after paying
If the figures are provisional, compare a conservative and favourable scenario and ask about the provider's processing deadline. If you have already paid, do not withdraw the excess yourself or carry it into the next year's calculation without checking. Ask the tax authority how to document a correction with the institution. Keep the revised figures, certificate and reply together. Until income is established, retain enough cash for social contributions, operating bills and household costs.
Separate the cash available from your estimated limit
In your year-end budget, keep two figures separate: the cash you can afford to lock away and the contribution your income may support. Suppose you estimate qualifying income of CHF 15,000. Applying 20% gives CHF 3,000, subject to the statutory ceiling and other conditions. If committing more than CHF 1,500 would dip into the cash you have set aside for VAT or social insurance, the higher calculation does not oblige you to pay the difference.
Keep a record of what changed
Reconcile your provisional accounts with the final assessment. Record which invoices were booked, which expenses were adjusted and what amount ultimately counted as qualifying income. If you paid into several 3a accounts, give your tax adviser the combined amount and the certificates for each payment. Multiple accounts do not give you multiple annual limits.