If the bookkeeper has already established in books receivables in earlier years for overpaid taxes the posting should be simple:
Cash:.............................................................................400
Receivables for overpaid taxes for real estate....................................300
Receivables for calculated interest:.....................................................100
If he hasn`t established receivables for it in previous years you should first correct the balance sheet for previous year and the opening balance of current year:
Receivables for overpaid taxes for real estate..............300
Receivables for calculated interest...............................100
Profit(revenue,capital)..........................................................................400
Than,in current year,after receiving the check you can post:
Cash:..............................................................................400
Receivables for overpaid taxes for real estate......................................300
Receivables for calculated interest........................................................100
You need also ,in second case, correct the Tax on the revenue for previous years