The tax assessor shall not receive commissions on errors made in assessments, on abatements or deductions from assessments allowed the taxpayer, nor on taxes on real estate bid in by the state at tax sales, nor on taxes which would be due on property except for the provisions of the law exempting homesteads from state taxes, nor shall he, after the abstract book has been turned over to the tax collector, receive commissions on any assessment to which an objection by the taxpayer, regularly entered, may then be pending, until such objection has been disposed of and proper assessment ascertained and determined.