From the mouth of Barbara Corcoran - Co-op Flip Tax

Q5 - Is there a cap on the flip tax a coop board can require on the sale of a coop?

A - A coop can impose any fees it wants and the so-called flip tax has become common in New York City coops as a way to shore up the building's reserve funds. The fees are structured as a percentage of the sale price or of the seller's profit, or in some cases a per share dollar amount or a fixed amount. But flip taxes can hurt the marketability of the apartments because if it's too high, buyers can avoid the building. So read the fine print and make sure it's not too onerous compared to other buildings.