I read a venue contract on Thursday that required a strict minimum guest count of one hundred and fifty people for a Saturday night wedding. My coworker signed it six months ago. She just got her final response cards back in the mail and only one hundred and twenty people said yes.
She assumed the venue would just lower the final bill and charge her for the people who are actually coming. They absolutely will not.
A minimum guest count is essentially a financial floor. The venue does not actually care if those thirty extra people show up. They just want the money those plates represent. If you fall short on people, you still owe the venue the exact same dollar amount. We spent two hours yesterday trying to figure out how to spend the difference so she did not just hand them cash for nothing. We ended up upgrading the entire bar package to top shelf liquor and adding a late night pretzel station that nobody really needs.
Never sign a contract with a minimum guest count you cannot easily guarantee. Ask the venue coordinator to write the initial contract for twenty percent fewer people than you are inviting. You can always pay for more plates later if everyone actually shows up.