1
general::
Phrase(s): fill the bill [and] fit 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.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
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]
American Heritage Idioms