Last year I began working as a contractor, for which I was required to make estimated tax payments and there was no withholding that I could set up through my employer (I received a 1099-Misc form stating my income instead of a W-2). My wife handled all of our finances/taxes when we were married, and overlooked paying estimated state taxes–only federal taxes were paid. Due to a number of things going on leading up to separating, we’d filed an extension for FY2009 taxes. We have now separated and have a signed + notarized agreement as of July 31, though just prior to moving out of state she filed her taxes as ‘Married Filing Separately,’ and will receive a small refund. In the separation agreement, it states that we will split 50/50 any tax refund, and also that “existing joint debts or tax obligations will be liable to both parties unless otherwise specified” (elsewhere it states we’re liable for the house, which is on the market; we indemnify each other from the other party’s individual debts too). She filed separately without consulting me first about it, though after going through the calculations of filing jointly and seeing that we would likely not get a refund; I had assumed we would file jointly, regardless of the outcome. Now, when I run some of the numbers, I don’t stand a chance of getting a refund when I file as ‘Married Filing Separately’ and will likely be looking at owing upwards of $3k when all is said and done, partially because no estimated state taxes were paid last year. Because I now have to file under this status, am I hung out to dry by myself on this probable tax obligation? Can she simply refuse to pay her part of the tax obligation (even though the money was used for joint benefit and had been going to a joint account) and there’s nothing I can do about it? Does it sound like she’s technically in breach of contract? Or am I probably screwed here?