I found out that my exh is doing this and is therefore paying less than 40% tax and also making CSA think that he is not as high an earner as he thinks. The difference is significant, think school fees for two per year.
I don't need the money to live since I work and take care of the children full time, it just seems a little off that he'd prefer to put money away instead of buying things for the children now, whilst they are small. It just left a bitter taste, since I have nothing left each month to even think about a pension let alone high contributions as all my money goes on the children.