After going through the grueling effort to file your tax return, you suddenly feel sick to your stomach as you realize that you made a mistake—don’t panic! Fixing a mistake on your tax return is actually a relatively smooth process. Here are is what is required for you to make any changes to your already filed tax return.

How to Fix a Miscalculation

If the mistake was something simple like an error in your math or you forgot to attach any necessary documents, then you don’t need to worry about amending your tax return. The IRS will usually fix the error and request any forms that are missing according to the article “Amended Tax Returns—How And When To File.” However, if this is not the case, then you will need to amend your tax return.

IRS Form 1040X: Amended U.S. Individual Income Tax Return

Now if the mistake is something more significant such as your filing status, change in your income, missed deductions or credits, then you will need to file an amended tax return. The form that you will need to use is the 1040X. Unfortunately, you cannot file an amended tax return online. You will need to file it on paper and mail it in.

If you received an IRS request for an amended tax return, then the address on that letter they sent you will be the place you can send your amended return. However, if that is not the case, then you will need to track down yourself the correct mailing address to send it to here. If the amended tax return requires any additional documentation, then make sure to include it. You may also amend more than just one tax return, but you will need to mail each one individually.

The deadline for amending a tax return is three years since the original filing date of your taxes or two years from the time you paid the taxes for that year. Whichever date is later is the one that you go off of. Typically, the process will take roughly 12 weeks to completely process. If you will end up with more money, you can cash the return you already received. On the flip side, if you end up owing more money, then you will want to jump on paying it off as soon as possible to avoid any penalties that may occur. To stay up to date on the status of your amended tax return, you can visit the IRS’ Where’s My Amended Return? tool.

If you are not sure if you need to file an amended tax return, then you should consult professional help. Hopefully, it is something as simple as a change in math and a simple document submission. However, if you would end up with more money than you were previously estimated, it is obviously in your best interest to start the amended tax return process as soon as possible.