179 expense deduction for a disposed asset, the depreciation reported as allowed or allowable on Form 4797 will include only the Sec. The Section 179 deduction allows businesses to deduct the full purchase price of qualifying equipment and software purchased or financed during the tax year.The Section 179 tax deduction allows companies to deduct the purchase price of new equipment. Enter as a negative amount the amount of Internal Revenue Code Section 179 expense deduction. A part of the IRS tax code, Section 179 allows businesses to deduct the full purchase price of qualifying equipment bought or financed during the tax year.