After an original tax return has been filed, it can only be changed by filing an amended return using Form 1040X. An amended return can be used to correct information on Form 1040. The following types of changes can be made by filing an amended return:
Reporting additional income
Claiming credits or deductions which weren’t originally claimed
Correcting mistakenly-claimed credits for which the taxpayer was not eligible
Changing filing status
Increasing or decreasing the number of dependents
Form 1040X Fees
If we (TFX) prepared your original return (and you require relatively few amendments), our fee for amending the original return and preparing the Form 1040X would cost you $150.
If the original tax return was prepared elsewhere (i.e., by another tax firm or you did it yourself), we’ll need to redo the actual return from scratch. Because all the figures in your tax return are related, even a tiny change may move you into a different tax bracket or change which deductions you’re eligible for. Amending a return prepared elsewhere involves the same work as preparing a brand-new return. Therefore, the fee is equal to the cost of preparing an original return ( TFX Pricing) plus the cost of amending the return and filing Form 1040X ($150).
Or, for other scenarios of amended returns, see this article.