IRS computers automatically place all refunds of $10 million or more on hold. They use this time to check for errors that may reduce the refunds. (Their version of low-hanging fruit.) But they are often late in reviewing the returns, so the held refunds collect interest.

When you've got over $10 million held, the interest can be signficiant. Treasury inspectors say that in 2008 the slow refunds cost the IRS $63 million in interest. The folks with the huge refunds got some extra interest, but taxpayers paid for it.

Taxpayers paid $63 million for the IRS being late. How much did taxpayers save from the IRS reviewing the held returns? No word from Treasury yet.

[On Fridays we explore the lighter side of taxes.]