My recommendation - contact the IRS. If you have been good about being in contact with them they will normally re-negotiate and allow you to delay the increase until you have resolved your issue with Social Security. Tell them what is going on, ask for a 30 day extension. Then if in 30 days if you still have not resolved the issue with SS contact IRS again. As long as you keep in contact and if possible continue sending them the $350 you have been doing to this point in time the likelihood is they will work with you.