Most mistakes in tax returns occur during the last two weeks of tax season before the deadline.
This is due to many people wanting returns and not enough time to both prepare the returns and allow for the taxpayers to review them prior to filing.
We recommend that, where possible, you have your tax professional file an extension for you and then finish the returns late April or early May – that way you will get their best service.
Also, remember that an extension is an extension of time to file, not an extension of time to pay – IRS charges ½ of 1% per month penalty plus interest on any unpaid balance after April 15th. California is the same except the first month the penalty is 5%.