National Pension Plan contributions or employment tax....?

Hi there, I have received for the past two years a small slip of paper from the "CIMIR" with a barcode and which appears to be a BE Govt based department.

From what I can see it shows what I've earnt (gross and net), any bonuses (13th month) received and the hours per week.

What are these actually for? Just proof that I've worked and paid tax, etc or is it towards the BE pension plan or something?

Thanks !