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# How is the CISSM calculated in Luxembourg?

The **Tax Credit for Minimum Social Wage (CISSM)** is a tax assistance that aims to guarantee tax neutrality for employees receiving a salary close to the minimum social wage, particularly during part-time work or temporary reduction of working hours.

To calculate the CISSM, you must first determine a **fictitious gross salary** based on the declared gross salary and the ratio between theoretical hours and actually worked hours.


## Calculation Method

**Calculate the fictitious gross salary** 
Fictitious gross salary = Gross salary × (Theoretical hours ÷ Actual hours)

**Check the applicable CISSM bracket**
* From 1800€ to 3000€: Fixed CISSM of **81€/month**
* From 3000€ to 3600€: Decreasing amount according to the formula → **CISSM = 81 / 600 × [3600 − Fictitious Monthly Gross Salary]**
* No credit granted for salaries below 1800€ or above 3600€

**Calculate the theoretical CISSM** 
Theoretical CISSM = (81 ÷ 600) × (Bracket ceiling – Fictitious gross salary)

**Prorate according to actually worked hours** 
Granted CISSM = Theoretical CISSM × (Actual hours ÷ Theoretical hours)


## Example

An employee receives a gross salary of **1947,50€**, with **96 actual hours** worked out of **168 theoretical hours** for the month of August 2025.

**Fictitious salary calculation**: 
1947,50 × (168 ÷ 96) = **3408,13€**

**Applicable bracket**: 
The fictitious gross (3,408.13€) falls between 3000€ and 3600€. 
→ Theoretical CISSM of **25,90€**

**Theoretical CISSM calculation**: 
(81 ÷ 600) × (3600 – 3408,13) = **25,90€**

**Proration**: 
25,90 × (96 ÷ 168) = **14,80€**

The **granted CISSM** for this employee will therefore be **14,80€**.


## Important points to remember

* CISSM guarantees an adjustment based on the fictitious gross salary.
* The calculation depends on the remuneration bracket in which the fictitious salary falls.
* The final amount is always prorated according to the hours actually worked.


## Source

* [ACD (Administration of Direct Contributions)](https://impotsdirects.public.lu/fr/az/c/credit-impot-salaire-social-minimum/cism2025.html)