Tax law gives relief to “illiquid” taxpayers, those with income or wealth but no cash. This relief results in revenue losses, creates opportunities for tax avoidance, and distorts economic decisions. And yet, we don’t know how much hardship is actually created by illiquidity. This Article provides a framework for determining the magnitude of that hardship. The framework reveals that the costs of selling property or borrowing money to pay taxes in cash are not the only costs borne by illiquid taxpayers; they may also have to make painful adjustments in their current consumption or retirement savings plans. These are the “quiet” costs of taxation. I show that illiquidity hardship can be quantified in dollar terms and thereby placed on the same scale as other considerations that go into the evaluation of tax law and policy, allowing it to be weighed in the balance and making it possible to identify the contexts in which it truly matters. I demonstrate that illiquidity hardship is a meaningful concern in the property tax context but is a weak justification for the “realization” requirement under federal income tax law.