<p>&lt;p&gt;If you discovered an error on a previously filed tax return β€” a missed deduction, wrong filing status, unreported income, or overlooked credit β€” you can correct it by filing &lt;strong&gt;Form 1040-X, Amended U.S. Individual Income Tax Return&lt;/strong&gt;.&lt;/p&gt;&lt;h2&gt;When to File an Amended Return&lt;/h2&gt;&lt;ul&gt;&lt;li&gt;You reported income incorrectly&lt;/li&gt;&lt;li&gt;You missed a deduction or credit you were entitled to&lt;/li&gt;&lt;li&gt;You used the wrong filing status&lt;/li&gt;&lt;li&gt;You received a corrected W-2 or 1099 after filing&lt;/li&gt;&lt;li&gt;You need to add or remove a dependent&lt;/li&gt;&lt;/ul&gt;&lt;h2&gt;When NOT to File 1040-X&lt;/h2&gt;&lt;p&gt;Do not file an amended return to correct math errors β€” the IRS fixes those automatically. Also, if the IRS sent you a notice correcting an issue, you usually do not need to amend.&lt;/p&gt;&lt;h2&gt;Deadline to File&lt;/h2&gt;&lt;p&gt;You must file Form 1040-X within &lt;strong&gt;3 years of the original return's due date&lt;/strong&gt; (or within 2 years of paying the tax, whichever is later). After that, you cannot claim a refund.&lt;/p&gt;&lt;h2&gt;How to File&lt;/h2&gt;&lt;p&gt;As of 2023, most 1040-X forms can be e-filed through tax software. Otherwise, mail the form to the address listed in the instructions based on your state.&lt;/p&gt;&lt;h2&gt;Processing Time&lt;/h2&gt;&lt;p&gt;Amended returns take up to &lt;strong&gt;20 weeks&lt;/strong&gt; to process. Track the status at IRS.gov using the Where's My Amended Return? tool.&lt;/p&gt;&lt;p&gt;&lt;em&gt;Source: IRS Form 1040-X Instructions; IRS.gov/amended-returns&lt;/em&gt;&lt;/p&gt;</p>