I have a client who just got a notice from the IRS for underreported income for 2022.  The brokerage 1099-B was for a joint account.  However, he and his wife divorced during the year.  So I reported half of the dividends, interest, and capital gains on each 1040 return.  Same with K-1s from a limited partnership.  I clearly marked (50%) on the Schedule B on each tax return.  What's the best way to respond to the IRS?  Is there a better way that it should have been reported so he didn't get stuck with all the taxes on the income? I use ProSeries Basic.