The Semi-Trailer Tax Parity Act would extend tax benefits related to floor plan financing to semi-trailers. Currently, certain interest deductions related to financing inventory are available for vehicles like automobiles and trucks, but semi-trailers are excluded from these rules. This bill would amend the tax code to allow semi-trailer dealers and manufacturers to deduct interest expenses on financing used to purchase semi-trailer chassis and bodies, treating them the same way as other vehicle types. The change would apply to tax years beginning after the bill is enacted and would primarily benefit businesses that finance semi-trailer inventory. No specific funding or appropriations are involved, as this is a tax code modification.