The deadline to file your income taxes if you applied for an extension was yesterday. Now, raise your hand if you left filing to the last minute – again. (Guilty) For anyone who rushed to get their taxes in on time before the 11:59 p.m. cutoff, they may have realized they might have made a mistake after submitting. Don’t worry, you don’t have to run to your local tax lawyer this instant, but you do have to take action. The sooner you correct your income tax mistakes, the sooner they will be resolved and the less you’ll owe to the IRS in fees and penalties.

Here’s what to do if you made a mistake on your tax return:

Option 1: If you make a mistake prior to the tax deadline

This is the best case scenario. If you submitted your taxes prior to the regular deadline of April 15, 2015, you can easily correct your mistakes by filing anew. Simply fill out a new tax return and either mail it in or file it electronically. You may have to wait some extra time to get a refund if you are owed any money, but it sure beats having to deal with corrections after the deadline, or even worse, receiving a notice from the IRS that they’ve made their own adjustments or informing you that you’ve been audited.

Option 2: For errors found post-deadline, submit an amended return

If you realized you made a mistake on your taxes and the deadline for filing has passed, you have the option to file an amended return. There are several things you can correct on a tax amendment form, including any wages, stock investments, or deductions you forgot to list. The only downfall to filing an amendment is that you cannot do it electronically. An amendment form must be printed out, completed by hand, and mailed to the IRS. This can be tricky, since many taxpayers use tax software, like Turbo Tax or H&R Block’s online portal, to e-file and these programs come equipped with several features that calculate credits and adjustments automatically.

Since a software program can’t help you out if you are filing an amended tax return, there’s a higher probability of making new mistakes that will tack onto your prior errors. To avoid additional mistakes, it’s a good idea to solicit the help of an accountant, tax preparer, or tax attorney when filing an amended return to prevent further complications.

Option 3: Wait it out

If you don’t want to go through the process of filing a new return or an amended return, you can always take a chance and wait to see what happens. Many times, the IRS will find the mistakes sooner than you may have, and will notify you prior to processing the return. This gives you the chance to correct any errors on your own.

However, you might receive a different kind of notice from the IRS informing you that they have already made the necessary changes and you may or may not owe more money. If you do owe money, you’ll be charged fees and interest based on the April 15 deadline. On the bright side, sometimes, the IRS corrects the errors and actually give you back a greater refund.

In the event that you are contacted by the IRS because of a mistake on your return, don’t panic, it happens all the time. Gather all your documents to support your position and either mail them in with the amendment or, if you object to the IRS changes, speak with an accountant or tax lawyer for further assistance.

Remember, time is not on your side. The longer you wait to fix a tax mistake, the more it can end up costing you. Take action as soon as possible to avoid additional charges.