Here is an Ad Hoc that shows you YTD w/ concession amounts.
LIST DA WITH CONCESSIONS > 0.00 WITH STATUS = 'P' AND WITH CLOSE_PERIOD BETWEEN %YEAR%01 AND %YEAR%12 BREAK-ON CONCESSIONS TOTAL UNITS TOTAL LISTING_COMM TOTAL SALES_COMM TOTAL CONCESSIONS
Now, this does not distinguish only buyer/seller concessions as the DA doesn't record what the concession is due to (it could be payment for a fee or warranty that MC/Agent agree to pay in order to make transaction happen).