Currently when you use a decentralized payment processor like Simplex or Moonpay to buy coins straight from your wallet, the wallet transaction only shows a deposit of the coin when purchased. I does not take into account the money used to purchase those coins so the fee charged goes ignored here. If we add support for those then you Fiat currency lost in the transaction will be included in your gain/loss calculations.
Hey! Thanks for the feedback! In ACCOINTING.com, we work based on a voting mechanism: the more upvotes your feature requests has, the faster it moves in our development pipeline. Hopefully, you’ll get enough upvotes from this community to have it implemented.