Each time I started up TaxCut while I was working on my taxes, it asked to check the website for updates. The reason: Tax laws change throughout the year.
My question is this: Is there a cut-off date where things are set in stone at the federal level for income tax rules?
I'm guessing it's no earlier than the end of January for the previous tax year (i.e., January 31st, 2010 for the 2009 taxes) because that's how long employers are given to send out W-2 forms. I suspect it can't be after April 15th, 2010, either. But where in between?

