give a blank check
give someone a blank checkand give a blank check to someone
1. Lit. to give someone a signed check that lacks only the amount or payment which can be filled in by anyone. Sally sent a blank check to school with Billy to pay for his books.
2. Fig. to give someone freedom or permission to act as one wishes or thinks necessary. He's been given a blank check with regard to reorganizing the workforce. The manager has been given no instructions about how to train the staff. The owner just gave him a blank check. Jean gave the decorator a blank check and said she wanted the whole house done.