My fiancée does not get her tax return because it is taken for her defaulted student loans. We will get married in July and would file married next year.

I make the vast majority of our household income (95%+). Can they take our joint return and can I prevent it? Would I be best off adjusting our withholdings to account for being married, the additional credits we will take and any other factors (we're buying a house next month and will be able to deduct prop. Tax and mortgage interest also) so our return nears 0 to minimize the amount the government can take on their terms?

Sorry for the long sentence... basically - I know it needs to be paid back, but I would rather pay it back my way instead of theirs.

And as an aside - anyone have any idea how I get the necessary information about paying it back, such as amount due and who to send payments to?

This is about 2009 taxes. Too early to give reply. Meanwhile you may read this: Your U.S. Tax Return: Filing Status for Married

You file Form 8379 as the "Injured Spouse" which will allow you to keep your portion of the refund.