Get your taxes done using TurboTax

Seems this is not such an unusual issue.  I can't be certain about my mother's liability for the obligation, but as she did not receive a 1099-C herself, when it appears other co-obligors have done so, I'm inclined to believe that she has no liability.  She may have been an additional card holder, but I don't think the application relied on her credit.  If true, would that give her secondary liability for his obligations?  Again, I would think not, but would appreciate your views.  Finally, is there a threshold below which the IRS likely not to pursue an action for the tax due on a forgiven indebtedness?  It feels like the filing requirements are somewhat overdone for modest amounts, but if required due they adhere to the same filing deadlines as individual tax returns?  If not, when must they be filed?  If so, can an extension be obtained even though a 1040 is not in issue?