401k match contribution for deceased employee on retro pay

Ok, this is a little strange and well outside of my wheelhouse; I would appreciate any input and a direction on where to begin.

An employee died in late 2021; at the time of his death a review was being conducted of his pay.  It was later determined that he had been underpaid and a retroactive pay order was going to be necessary; a large retroactive pay order.  A portion of this pay will be a 401k employer 2% contributions.

Because final wages to the employee will not be paid during the year he died, the wages aren't subject to FITW.  We are unsure how this affects calculating 401k contributions.  Again, this is well outside of my wheelhouse and I do not know where to begin.  I appreciate any and all input.

sbuck, is the underpayment determination based on a legal analysis, e.g. wage and hour violation regarding overtime or the like, or other misclassification? Or because of a mistaken calculation of a formula bonus or the like? If so, then this is back pay and although the usual caveats apply (i.e., review your plan document, you are not giving me all of the facts, etc.) I think the wages will count for 401(k) as if they had been paid when they were supposed to be. See, e.g. 1.415(c)-2(g)(8). There's a DOL reg that really governs, but I forgot the section #. Maybe someone else will provide it.

The alternative is that after the guy died they though, "Gee, he really was a great employee and we should have paid him more, even though we did not have to." If they are doing it for a reason like that, I think the treatment would be different. Get's complicated.

The underpayment was due to a his not having received automatic pay raises due him; he earned the money and due to a misclassification that was not caught, he was not paid the correct amount.