In fact, California tax officials have now pegged an exact amount to that bond: $37,712.71.
That's the amount the ex-couple has been slapped with in a tax lien filed Tuesday by California's Franchise Tax Board over unpaid taxes for 2004.
The tax document also cites the couple's former Encino, Calif., home as their last known residence.
Britney's camp appears confident that star will eventually be in the clear. "The lien is erroneous and will be rectified," her rep tells E! News.
Of course, 2004 was a particularly memorable—and lucrative—year for the pop star: Her 55-hour wedding to Jason Alexander that January was annulled, and she and Federline tied the knot later that fall.
That year, she also released her first fragrance, followed by a greatest-hits album powered by her remake of Bobby Brown's "My Prerogative."
Her next prerogative, we're guessing, is to figure out how to deal with her and K.Fed's current tax headache.