 The IRS is the most powerful collection agency on earth. And if you owe back taxes, the news isn't good. The IRS is raising the interest rate it charges on unpaid taxes. And further rate hikes are expected. Most people don't know it, but the IRS adds interest charges on your tax debt daily. So if you owe the IRS today, you will owe even more tomorrow. And it doesn't stop until you get right with the IRS.