You are the executor so you get to make this decision. The refund and interest earned should definitely be used to pay any debts of the estate (like the taxes you paid).
If there is the potential for more debts to pop up then you may want to hold the money in the estate until those are paid.
If you are reasonably comfortable that all debts have been taken care of then it is fine to transfer the money and shut the estate down.
@HydroSci
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
