Just a thought, when you enter the property tax, if you use the purchases journal, you could enter the entire amount on one line and on the next line enter the negative amount as a discount.  

I agree with BethMW... with a bit of further explanation.  To have the $4870 show in the financial statements, the discount will have to be entered to a line other than 'property tax expense'.  Perhaps an income line such as 'miscellaneous income' or 'property tax exemption'.

as C White said create (or check chart of accounts) to see if there is a 1000/5000 account for the property tax discount.  create you je or invoice.  

example for invoice

property taxes                     $5000        accnt number 5212 

property tax reduction        -$4760        accnt number 5213 or could be a 1000 account 

subtotal                               $240.00

also you could refer to previous years to see how it was done also then