When your tax return is amended, it means you have realized some errors in your previous tax return, so you decide to file again for that year to correct any mistakes made the first time. Mistakes could be anything such as false information, an error in income reported, a failure to list your dependents (which doing so leaves you out of some nice benefits), and more. These are almost always accidental mistakes that must be justified as accidents, and corrected. With that said, if you amend your tax return, the section 179 can be reduced. Section 179 under the IRC means a taxpayer can deduct the cost of their property on the income as an expense. Amending you tax return to fix accidental mistakes allows you, as a taxpayer to do that. It would be wise for you to hire a tax preparer or accountant to help you with this process, as it can be complicated to some.