Must a Father pay the Sadaqatul Fitr on Behalf of his Children who are already of Age?

Question: What do the Ulema of Deen and the Muftis have to say about the fact that just as one cannot pay another person's zakaah without his permission, one can also not pay another person's Sadaqatul Fitr without his permission? It is common here for fathers to pay Sadaqatul Fitr on behalf of their children who are already of age. Similarly, husbands pay the Sadaqatul Fitr on behalf of their wives. Is the Sadaqatul Fitr valid? Is it necessary for the children and wives to make the men their representatives to pay the Sadaqatul Fitr for them?

Answer: Yes, this rule applies to the Sadaqatul Fitr as well. Permission is necessary to pay the Sadaqatul Fitr. However, because the amount is not substantial, men usually pay the Sadaqatul Fitr on behalf of those children whom he still supports and on behalf of his wife. The permission is generally taken for granted and the act is therefore regarded as permissible in the best interests of people.

On the other hand, because the zakaah amount is more and unspecified because people usually do not pay on behalf of others. it will be necessary issue express permission or necessary to appoint the person as a representative. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.3