Is it permissible for a customs officer to take money from a taxpayer without compulsion or prejudice to the public interest, and is it permissible to donate some of this money as charity?

Imposing customs duties on Muslims is of two types:

The first: Permissible if it is in exchange for services or due to the state's need for public interests.

The second: Forbidden if it is not in exchange for services, or if it is in exchange for services whose value does not reach the amount taken, and the state does not need this money.

Accordingly, if imposing customs duties is permissible, then your work and taking wages for it are permissible, and charity from this money is valid.

But if imposing them is forbidden, then it is not permissible for you to work in it, nor to claim wages, nor is charity from this money valid, because it is illicit (khabith).

As for claiming money from individuals without a legitimate service in return, it is not appropriate. And if it is in exchange for a service that is part of your work, then it is not permissible because it is a bribe.