When it comes to filing tax extensions, it is always better to be safe than sorry. Laws vary from state to state with some states simply accepting an IRS form 4868. However, the rules are varied and complicated, so if you are planning on filing an extension on your taxes, carefully review your state's laws.
According to the Connecticut Department of Revenue Services, "after taking into account any Connecticut income tax withheld from your wages or any estimated Connecticut income tax payments you have made (or both), and you have requested an extension of time to file your 2009 federal income tax return, you are not required to file Form CT-1040 EXT."
However, if you underestimate your taxes by $1, you could theoretically be on the hook for a late filing penalty in addition to any penalties owed on the underpayment of taxes due by April 15th.
According to the State of California Franchise Tax Board, "California gives you an automatic filing extension through October 15, 2010. You don't need to apply for one." However, you must file an IRS form 4868 and pay all taxes due to avoid late payment penalties.
If you are planning to utilize tax extensions this year, be sure to consult your state's tax revenue department website for full details. And, if you owe taxes, be sure to pay them on time, even if this means using a credit card and paying a 2-3% fee. Owing money to your credit card company isn't a great thing, but nothing is worse than owing money to the IRS.