What is the origin of the idiom "blank check" and when to use it?

The origin of the idiom "blank check" can be traced back to the practice of signing a physical check without specifying the amount, allowing the recipient to fill in the desired sum. This literal concept of a blank check evolved into a metaphorical expression, symbolizing the granting of complete authority or freedom to someone. The idiom emphasizes the idea of trust and confidence in the recipient's judgment, as they are given the discretion to make decisions or take actions without preset limitations. It highlights the notion of unrestricted power, autonomy, and the absence of specific instructions or restrictions. It is commonly used in discussions about granting wide-ranging autonomy, particularly in politics, business, or personal relationships.