When you owe back taxes to the IRS and you can't afford to pay it back in full, the most critical aspect of your case is: How much can you truly afford to pay back? In order to determine the amount you can afford to pay, the IRS uses two calculations. One is the income and assets you have available to pay. The other is what expenses the IRS will allow. A taxpayer who owes money to the IRS can use necessary expenses, may be allowed conditional expenses, and may even be allowed miscellaneous expenses.
To illustrate the point, a US tax court case demonstrates that just because something is necessary to a taxpayer, does not mean that that IRS will feel the same way.
In George Thompson v. Commissioner, the taxpayer claimed two expenses that should be "allowed expenses." One was his monthly tithe (or donation) to his church, the other, his college expenses for his children. Claiming these expenses would reduce the amount he would ultimately pay back to the IRS through a partial payment installment agreement. On his Form 433a he included both expenses, and wanted the IRS to reduce his monthly payment by the amount of these expenses.