What is the ruling on taking an end-of-service bonus (severance pay) from an interest-based financial institution?

It is well-known that working for interest-based institutions is forbidden, and the resulting salary is ill-gotten. This grant (bonus) is either explicitly part of what the employee is entitled to for their work in the institution according to the employment contract, or it has become customary, like a retirement pension, or it is a non-binding gift from the institution.

Based on the first possibility, it is forbidden to take it, unless one is poor and in need, in which case they may take only what they need and spend the rest on charitable causes.

Based on the second possibility, it is a gift from mixed funds, and there is no harm in taking it.