Credit given to the buyer at closing should have been included in the HUD-1 , closing statement -- not on the 1099-S. If however, this adjustment was kept out of the settlement statement ( HUD-1) , for whatever reason, then you enter this as cost of sales -- like commissions, transfer taxes,.... misc. expenses. As mentioned by @KittyM , this would reduce your sales proceeds ( NOT your COST Basis ) and thus reduce your gain ( capital or ordinary ). Does this help ?
