The payment of principal is never a deductible expense. However, check the payoff information to see whether there were any fees paid in addition to principal; the fees may be considered a selling expense.
Advance payment of current tax liability based either on wage withholdings or installment payments of your estimated tax liability. To avoid penalties, you generally must pay to the IRS either 90% of your final tax liability, or either 100% or 110% of the prior year’s tax liability, depending on your adjusted gross income.