The phrase "blank check" means giving someone complete freedom and authority to do whatever they want without any limits or restrictions. Full definition
It is known as a «blank check company,» because investors buy into the fund without knowing which company they will end up owning a part of. (inc.com)
As you may know, many credit card lenders freely offer these to their customers with good credit, in the form of blank checks the borrower is invited to use as they wish. (mortgageloan.com)
In other words, companies with no profits or specific prospects have raised $ 14 billion in blank check funding. (etfexpert.com)