US taxpayers owe almost $700 million more in interest every month it delays IEEPA refunds

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Sources: Penn Wharton Budget Model; authors' calculations applying interest formula from CBP and interest rate from IRS.

Note: Interest is calculated daily using compound interest formula of:
(((1 + (RATE/NBR OF DAYS IN YR)) ^ NO OF DAYS) - 1) MULTIPLIED BY IEEPA TARIFFS COLLECTED.
To keep estimates conservative, authors apply the 4.5% rate for large corporate overpayments, even though the first $10,000 of each overpayment earns 6%. We also assume all tariff collections occur on the last of each month, so no interest accrues within the month of collection.
This chart has been updated to reconcile Penn Wharton's IEEPA collections estimate of $164.7 billion with CBP's declaration that those collections totaled $166 billion.