Hello,
I would like to clarify what you mean when you say you made a mistake in fiing an extension.
Do you mean that you did not file an extension?
Filing an extension means that you have an extension of time to file your return.
However you do not have an extension of time to pay your taxes. You should estimate the amount of tax due at the time of filing the extension and make a payment at that time to avoid the failure to pay penalty.
You can still file your tax return by the extension date and pay the taxes due by then. However you will be subject to the the penalties for filing and paying late. There will also be interest on the balance due.
You have until October 15 to file your return and pay your balance due.
I hope this answers your question.
Mary, Tax expert
If the situation is that you made a mistake when you filed your extension by not paying enough taxes and there fore still have a balance due, you would just owe additional underpayment penalties and interest on the difference. You can consider annualizing your income.