The problem: Urssaf doesn't recognize half hours
A real schedule isn't always a round number. An employee might work 21.5 hours in a month: a few hours on Monday, a morning on Wednesday, and a total with a fraction.
The cesu.urssaf.fr website, however, only allows you to enter a whole number of hours. No decimal points, no minutes. Faced with 21.5 hours, you must declare 21 or 22.
This is what Urssaf calls hour splitting, and they have published an official method for handling it without the employee losing anything: how to declare split hours.
The method: round down the hours, adjust the rate
The principle chosen by Urssaf is not to round to the nearest whole number, but to always round hours down to the nearest whole number, then increase the hourly rate so that the net amount paid to the employee remains identical to the cent.
Concretely, for 21.5 hours worked at 15 € net per hour:
- Net salary actually due: 21.5 × 15 = 322.50 €
- Hours declared: 21 (only the whole number part is kept)
- Declared hourly rate: 322.50 ÷ 21 = 15.357..., rounded up to the nearest cent to 15.36 €
- Declared amount: 21 × 15.36 = 322.56 €
The employee receives 322.56 € instead of 322.50 €: never less, sometimes a few extra cents thanks to rounding the rate up to the nearest cent. This is the rule that governs the entire mechanism: splitting hours must never disadvantage the employee.
How Kiwisio applies this rule
You don't have to do any calculations. Every month, Kiwisio compares your actual hours to the nearest whole number of hours rounded down. As soon as it detects a difference (21.5 h, 15.25 h, or any other fraction), it automatically recalculates the hourly rate to declare so that the final amount covers exactly, to the cent, what you owe your employee.
This calculation appears directly in your monthly summary, in the form of the hours and hourly rate to copy directly into cesu.urssaf.fr. As soon as an adjustment has been made, an explanatory box appears:
Hours and rate adjusted: Urssaf does not accept fractional hours. The total remains identical.
This gives you the certainty that your employee receives the full net salary due for the month, down to the cent, without ever having to check the calculation yourself.
Why not simply round to the nearest whole number
Rounding 21.5 hours up to 22 might seem more natural, but it would create another problem: the employer would then pay social contributions on half an hour that wasn't actually worked, and the declared amount wouldn't match the actual working time. Always rounding down to the nearest whole number and then compensating on the rate ensures that:
- the declared hours always correspond to time actually worked,
- the employee receives the full amount due, without unfavorable rounding,
- the calculation remains verifiable: declared hours × declared rate always results in an amount consistent with the actual net due.
This is the consistency that Kiwisio automatically checks every time a summary is generated, even before the declaration is submitted.