When income tax is unpaid, interest generally accrues from the tax return due date. After notifying a taxpayer of a deficiency, the IRS may abate the interest if delays are caused by the tax agency. In one case, a man failed to pay taxes on the sale of his business. Prolonged investigations added years to the interest accrual period. When the taxpayer was given the final bill, he was told that interest would stop accruing if he paid the balance. He didn’t pay, and filed a claim for abatement, citing “arbitrary delays by the IRS.” The IRS denied his claim. The U.S. Tax Court ruled the delay was justified and the IRS hadn’t abused its discretion by denying the abatement. (TC Memo 2019-99)