Health Contribution Assessment: Which Base to Retain (and Why Prorating Poses Risks with URSSAF)
When your collective agreement refers to the “fixed gross base salary”, the health contribution is calculated on the contractual salary — and especially not on the reduced compensation due to an absence. Prorating this base leads to under-contribution… and exposes you to a potential URSSAF reassessment. Here is the rule and the method for configuration.
This article is part of the Payroll Law: The Employer’s Guide.
The Base to Retain: Contractual Fixed Gross Base Salary
When the collective agreement refers to the “fixed gross base salary” (a common wording, for example in certain collective bargaining agreements (CCN) for service providers), the health contribution is calculated on the contractual base salary, regardless of monthly variations.
Example: for a contractual base salary of €4,000, the contribution is calculated on €4,000, even if an absence reduced the paid salary to €3,300 (subject to the collective ceiling, often expressed as a percentage of the A tranche of the monthly Social Security ceiling).
Why? The term “fixed” opposes any variation: bonuses, increases, overtime, or complementary hours, and temporary variations due to absence. The text expressly excludes these accessories (“excluding bonuses, excluding increases…”). A strict interpretation is necessary: if the social partners had wanted a prorated base, they would have referred to “the compensation subject to contributions” or a base “prorated in the case of absence”. In the absence of such terminology, the fixed gross base salary cannot be substituted by the social base of the month.
The URSSAF Risk of a Reduced Base
Retaining €3,300 instead of €4,000 leads to a reduced contribution for both employee and employer to the system. However, the employer’s contribution to fund supplementary health insurance represents a benefit, part of which is reintegrated into the CSG/CRDS base (General Social Contribution / Contribution for the Repayment of Social Debt). A reduced contribution may therefore result in a social loss — and pose a risk of reassessment in the event of a control. Retaining the contractual reference base secures the social treatment.
Caution: check the insurer’s notice or the collective contract — a clause may adjust the calculation in the event of contract suspension. In the absence of contrary stipulations, the calculation on the non-prorated contractual base salary is the most robust option.
Configuring Bases: CCN by CCN
Do not look for a standard “unified” base. The texts may be hybrid (the same article may refer to “gross salaries subject to contributions” while excluding overtime, bonuses, allowances, in-kind benefits, and professional expenses).
Method: define a reference base (PMSS, gross subject to contributions, or base salary), then apply inclusion/exclusion rules for each payroll item, according to the collective agreement, the implementation act, and the insurance contract.
Frequently Asked Questions
Prorating in case of absence? No, base = contractual base salary.
Why a URSSAF risk? Under-contribution → impact on CSG/CRDS → potential reassessment.
A base for all CCNs? No: reference base + rules by item.