The tax issue suggested by the situation is:
1. Can the IRS assess back taxes for the first five years in which Mr. Tillotson did not pay income tax or file a tax return?
Additional considerations related to this issue may include the statute of limitations for assessing back taxes, potential penalties and interest for late filing and non-payment, and the consequences of failing to comply with tax obligations for an extended period of time. It is important for Mr. Tillotson to seek professional advice from a tax attorney or a qualified tax professional to understand his rights and responsibilities in this situation and to determine the best course of action to resolve any potential tax issues.