Marie Curie Postdoc - Employer contribution in Spain

Hi all,

I recently started a Marie Curie postdoctoral fellowship in Spain. Looking at the first payslips I realised that my salary is taxed twice, first by the institution (so called "employer contribution") and then by the Spanish government.

The employer contribution (which in the payslip is found under the "social security") for 2025 is calculated as 32.07% of almost all the gross salary (there is an upper threshold close to the total value of the gross salary) and it is applied to living, mobility and family allowance. On the remaining amount the regular Spanish tax rate, close to 27% for 2025, is applied.

I have two questions:

1) has anyone ever experienced the same fiscal regime and deductions for their Marie Curie postdoc contract, especially in Spain?
2) supposing that the employer contribution should come out of the institution instead of the living allowance (which, given the name, would be reasonable), what action can be taken? Has anyone ever appeal to the project officers through the portal of the European Commission?

P.s. I updated the Excel spreadsheet (https://docs.google.com/spreadsheets/d/1lAvl4xhUmzU8c9fCGDx7cFM2PQUT1Je-/edit?pli=1&gid=1210481379#gid=1210481379) created by Juan Manuel which seems a great idea to compare tax rates and deductions.