Section 1449-BBBBB. Imposition of tax

Notwithstanding any other provisions
  of law to the contrary, the county of Tompkins, acting through its local
  legislative body, is hereby authorized and empowered to adopt and  amend
  local  laws  imposing  in  such  county a tax on each conveyance of real
  property or interest therein when the consideration exceeds five hundred
  dollars, at the rate of one dollar for  each  five  hundred  dollars  or
  fractional  part  thereof.  Such local law shall apply to any conveyance
  occurring on or after the first day of a month to be designated by  such
  legislative  body, which is not less than sixty days after the enactment
  of such local laws, but shall not apply to conveyances made on or  after
  such  date  pursuant  to binding written contracts entered into prior to
  such date, provided that the date  of  execution  of  such  contract  is
  confirmed by independent evidence such as the recording of the contract,
  payment  of  a deposit or other facts and circumstances as determined by
  the treasurer.