fill the bill, to

To be helpful, useful, or what is needed in a certain situation. A: "I need another string of lights." B: "Will this one fill the bill?"

to be acceptable. Jane: I need some string. Tom: Here's some twine. Will it fill the bill? I need cloth to make a shirt. This muslin ought to fit the bill.

Serve a particular purpose well, as in I was afraid there wasn't enough chicken for everyone, but this casserole will fill the bill , or Karen's testimony just fills the bill, so we're sure to get a conviction. This expression alludes to adding less-known performers to a program (or bill) in order to make a long enough entertainment. [First half of 1800s]

To serve a particular purpose.

To satisfy the requirements, to suit a purpose. This term originally came from the nineteenth-century American stage, where the posters announcing a program would list the star attractions and then add lesser-known entertainers to complete the show (or fill out the bill). By mid-century the term had been transferred to other areas, where it acquired a more primary sense of providing what was needed. Thus a political article in Harper’s Magazine in 1890 included the comment. “They filled the bill according to their lights.”