Section 1449-BBB. Imposition of tax

Notwithstanding any other provisions of
  law  to  the  contrary,  the  county of Nassau, 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 five dollars for each five  hundred  dollars  or
  fractional part thereof.  The authority of the county to adopt and amend
  local  laws  imposing  the  tax  authorized  by  this  section  and  the
  imposition of  all  taxes  pursuant  thereto  shall  expire  on  January
  thirty-first,  two  thousand  one.    Such  local  law  may apply to any
  conveyance occurring on or after the date designated by such legislative
  body, 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.