Corporations may be missing out on refund opportunities if they do not act prior to March 15th!
If it was determined that your corporation overpaid state tax in prior years, and this same error was made each year for several years, then your corporation may want to file amended returns to obtain refunds. However, the number of years for which your corporation could file amended returns would be limited by the statute of limitations.
Most state's statute of limitations (or time period for filing refund claims) last either three or four years from the later of the original due date or the date the return was filed, or some other variation. Each state is different, so it is important to confirm the statute of limitations for the states you are dealing with.
For example, New York's statute of limitations is the later of three years from the date filed or two years from the date paid. The original tax return for calendar tax year 2008 would have been due March 15, 2009. Therefore, if the original return for 2008 was filed (and the tax was paid) by March 15, 2009, New York's statute of limitations for filing refund claims for the 2008 tax year would expire on March 15, 2012.
This analysis should be done for each state for which a refund claim (amended return) is desired to be filed.