As indicated in section 6.6 of the directives concerning withholding taxes in the Canton of Geneva, the salary certificate can be used as a withholding tax receipt if certain information is included in section 15.

The trigger for this printout can be found at the employee level in tab 6 (Salary certificate - Texts and amounts).

or in the  the company settings to do so in a global way. (It will only do so for people concerned by the canton of Geneva)