Nassau’s financial control board is warning the county not to pay vendors for work done before contracts are approved, weighing in on a controversy that has caused a rift between Republican County Executive Edward Mangano’s administration and GOP county lawmakers. The Nassau Interim Finance Authority last week added language to its contract approval forms that explicitly states its guidelines on vendor payments. It says: “NIFA approves this contract/amendment, but no time charges shall be recognized or paid for services rendered prior to” the agreement’s final execution. NIFA counsel Jeremy Wise said the board took action because Nassau had allowed work to begin on numerous pacts before they’d come before county legislators. The county this month identified 47 such contracts, some dating back eight years. … The county administration for years has allowed some vendors to start work without legislative approval, but the practice began generating consistent complaints from GOP lawmakers only in the last month. … But [county procurement compliance director] Cleary said the problem isn’t unique. New York City, where Cleary worked previously, reported more than 600 retroactive contracts in 2013, records show.