Child support is not taxable; you do not enter child support received in the income section on your tax return. The only place you may want to enter it is for the sales tax deduction.
You can enter the sales tax you paid in 2018 by going to Federal>Deductions and Credits>Estimates and Other Taxes Paid> Sales Tax.
Sales tax is an itemized deduction. If your state has a state income tax, you have to choose between using the deduction for your state tax paid OR the sales tax deduction, whichever is higher. The TT process will suggest one or the other as you prepare your return. Under the new tax law, there is a $10,000 cap on the total of sales tax, and state and local taxes (SALT) that you can use.
“Major purchases” that you can enter for the sales tax deduction include:
Motor Vehicles (cars, trucks, motor homes, RV’s, sport utility vehicles and off-road vehicles
Aircraft or boats
Building materials for major home improvements
You cannot deduct: furniture, jewelry, home electronics such as TV’s or computers