In case of tax payment no rewards. Bet it ITR or ATAX
You are right, most banks are excluding government payments from being rewarded. There are a few banks which are still rewarding, one might want to use them while they last. Example StanC still rewards, sc smart might be preferable for 2% rewards max 1k a month. Idfc, AuBank etc still rewards afaik. Sbi simplyclick gives 5X RP too, last I heard.
Charges are shown before selecting the pg itself, if you don’t see the charges getting added while paying on PG, there’s high chances it will get added latter on (heard from many for HDFC pg)