The federal government paid taxpayers $10.2 billion in interest payments for delayed tax refunds last year, more than triple what it shelled out just a couple of years ago.

The dramatic run-up in costs reflects the steep rise in interest rates over the past few years, but it is also a marker of the economic toll taken by delayed refunds and the IRS’s inability to keep up with its workflow. The agency’s struggles, which can harm businesses and families desperate to get their money back, have prompted Democrats to approve vast new funding to increase its workforce, and they have even led to some GOP support for giving it added resources.