Self-employed professionals: how to set tax and AVS advance payments without unpleasant surprises

For a self-employed person, the unpleasant tax surprise usually does not happen because the tax rate changed overnight. It simply comes from advance payments based on an old activity, while profit has increased, family situation has changed, or the social security fund is still working with an unrealistic estimate.

Advance payments are not a definitive prediction. They are provisional amounts intended to best follow the current year. They can — and sometimes must — be adjusted. It is important not to confuse revenue, the profit used to assess social security contributions, the taxable income of the household, and the available cash flow.

The method below applies to individuals recognized as self-employed by a compensation fund. Since tax rules vary by canton, the procedures and interest rates in Vaud are used as a concrete example.

Who is concerned?

The status of self-employment does not arise from the title on a business card or from the fact of invoicing one's services. It is recognized by the compensation fund based on the concrete situation: activity carried out in one's name and for one's account, economic risk assumed, own organization, and, in principle, a plurality of clients.

The operator of a sole proprietorship and certain partners of partnerships can be self-employed. In contrast, a shareholder of a corporation or a partner of a limited liability company who works for their company is considered an employee of that company for social insurance purposes. The distinction is developed in our article. Sole proprietorship or LLC: when should you change structure?.

Two different calculations: AVS on one side, taxes on the other.

A common mistake is to transmit the same amount to the AVS fund and to the tax administration. The two institutions do start from common data, but they are not looking for the same thing.

A tax change does not automatically update the AVS, and vice versa. Two separate procedures must be carried out.

How to estimate the AVS advances in 2026?

The fund sets the advances based on the estimated income of the current year. The final contributions will be calculated later, when the tax authority has communicated the actual income and the own capital invested.

Exception to know: when the self-employment activity is secondary and its annual income does not exceed CHF 2,500, contributions are generally only collected at the request of the insured. The activity must still be reported so that the fund can examine the status.

The rate of 10% does not necessarily represent the entire bill. Contributions to family allowances and administrative fees, as well as any cantonal contributions, are added. In the canton of Vaud in 2026, the Cantonal Fund indicates a contribution to family allowances of 2.95% up to CHF 148,200 of income, a PC Families contribution of 0.09%, and administrative fees ranging from 1.5% to 5% of the AVS/AI/APG amount.

The final calculation also includes technical adjustments: tax-deductible personal contributions are added to net income and interest on invested equity is deducted. For a serious estimate, it is therefore preferable to use the official calculator or request a simulation from the fund rather than mechanically applying 10% to the accounting profit.

The threshold of 25% is not a comfort margin.

The self-employed person must report a significant change in income. If the payments made do not reach 75% of the final contributions, late interest of 5% may be charged. Ordinary payments are generally billed quarterly and must reach the fund no later than the tenth day following the end of the quarter.

One sometimes hears: "My profit is not yet certain, I will see at the closing." The objection is understandable, but the fund can respond that uncertainty does not prevent updating an estimate that has clearly become outdated. A more cautious internal rule is to review the file as soon as a lasting change of 10 to 15% appears, without waiting for the sensitive legal threshold.

How to set tax payments?

The tax is not calculated solely on the company's profit. It is necessary to reconstruct the overall taxable income: independent profit after tax corrections, spouse's income, income from securities or real estate, then personal and social deductions. For cantonal and municipal tax, the taxable wealth and the municipality of residence must also be taken into account.

In the canton of Vaud, the official calculator allows for separate estimation of the ICC and the federal direct tax. It requires the taxable ICC income, the taxable IFD income, wealth, marital status, children, and the municipality. Deductions can significantly alter the estimate; our article on the deductions to check in the Vaud tax declaration provides the main points of attention.

The Vaud ICC is paid in twelve monthly installments, from January to December. If the installments no longer correspond to the current situation, an adjustment can be requested at any time with e-ACO. One should not simply modify the amount of the QR-invoice in e-banking: the request must be addressed to the administration so that the new installments are formally determined.

In 2026, the canton of Vaud applies a late interest of 4% on unpaid, late, or incomplete installments. The interest on early payments is 0%, while the compensatory interest is 0.125% when the payments due on the general deadline of March 31 do not correspond to the tax ultimately owed. A massive overestimation is therefore not necessarily useful: it is often more rational to make realistic installments and maintain a safety margin in a separate bank account.

Example: transform the estimate into a cash flow plan

A Vaud independent retains, after updating her accounting, a determining estimated AVS income of CHF 100,000 for 2026. For reference, and without considering a particular situation :

After taking into account other income, wealth, the municipality, and deductions, the tax calculator estimates the ICC and the IFD at CHF 18,000. The independent retains an internal margin of 10 %, which is a tax reserve of CHF 19,800. Her target annual reserve thus reaches CHF 33,090, corresponding to CHF 2,757.50 per month.

This monthly calculation is a cash flow rule, not the official invoice schedule. The AVS installments remain quarterly, the Vaud ICC monthly, and the IFD is subject to separate monitoring. The safety margin remains in the reserve account as long as it is not needed.

The practical method in six steps

1. Keep the accounting up to date. An estimate based on six months of accounting delay remains mainly a well-presented intuition.
2. Project the annual profit. Add the realized result, reasonably foreseeable mandates, and still expected charges. Isolate the VAT, which is not a disposable income.
3. Estimate social contributions. Use the 2026 scale and add the cantonal contributions as well as the cash fees.
4. Reconstruct the household's taxable income. Integrate other income, wealth, deductions, and family situation, then use the cantonal calculator.
5. Compare with the installments already invoiced and paid. Measure the AVS gap, the ICC gap, and the IFD reserve separately.
6. Adapt and document. Inform the fund, submit the tax application, and keep the calculation that justified the new amounts.

The control should be carried out at least at the end of each quarter, but also after the loss or gain of a major client, a work incapacity, a major investment, a family change, or a significant margin variation.

The most costly mistakes

• Calculate a percentage of the turnover. Two activities with the same turnover can have radically different profits.
• Confusing profit and cash. A received invoice, an investment, or a loan repayment do not all have the same tax treatment.
• Forget the spouse's income and wealth. They do not necessarily influence the AVS of the activity, but can significantly alter the tax.
• Only budget the 10% AVS/AI/APG. Family allowances, cantonal contributions, and administrative fees are added.
• Reduce a tax installment by yourself. In the canton of Vaud, a formal modification of the installments must be requested.
• Wait for the final taxation. At this stage, the catch-up is certain and the possibilities of spreading do not necessarily eliminate the interests.

The opposing viewpoint: should we intentionally underestimate?

Keeping low down payments leaves more cash in the business. This choice may seem rational when the activity is volatile. However, it is only defensible if the transmitted estimate remains credible, if the corresponding reserve is not spent, and if the interest costs are accepted.

The administration or the fund may argue that an updated accounting revealed a sustainable increase and that the independent contractor needed to adjust their down payments. Conversely, overpaying significantly is not optimal when the interest earned is zero. The reasonable solution is therefore to aim accurately, to maintain a private margin, and to document the assumptions.

How Delta Conseil SA can assist you

Delta Conseil SA can establish an interim accounting situation, project the annual profit, simulate social and tax charges, prepare modification requests, and build a cash flow plan adapted to the collection rhythm of the activity. The follow-up can be occasional or integrated into a quarterly review.

Frequently asked questions

Can you modify your down payments multiple times during the year?

Yes. A new estimate can be provided when the situation changes. In the canton of Vaud, e-ACO allows for a tax adjustment to be requested at any time; the AVS fund must also be informed of any significant variation.

Does a decrease in tax prepayments automatically reduce AVS prepayments?

No. The bases and authorities are distinct. It is necessary to contact the tax administration and the compensation fund separately.

Should 30% of the profit be systematically reserved?

There is no universal percentage. The need depends on income, family situation, wealth, municipality, deductions, canton, and additional contributions. A flat rate can serve as a temporary safeguard, not a definitive calculation.

Does the owner of an LLC pay independent AVS prepayments?

In principle, no for his activity in the LLC: he is an employee of the company and contributions are deducted from his salary. However, he remains personally taxed and may have other independent income.

What to check when the final taxation arrives?

It is necessary to reconcile the retained profit, social contributions, deductions, and the credited prepayments. The appeal period is short; our article on the checks to be made upon receiving a Vaud tax decision presents the procedure.

Official sources

• Regulation on AVS (RAVS), notably art. 24, 25 and 41bis
• AVS/AI Information Center, memo 2.02 — Contributions of the self-employed, status January 1, 2026
• Federal Office of Social Insurance, overview of contributions
• Vaudoise Compensation Fund AVS, self-employed
• Canton of Vaud, determine or modify your payments with e-ACO
• Canton of Vaud, personal income tax calculator
• Canton of Vaud, tax payment and interest rates 2026