When someone sends you crypto on your receive address to your exchange, how does the exchange know if these funds are to be taxed or not when they prepare the forums at the end of the year?
The exchange does not care about it. They only need their customers to use their exchange for trading, and get trading fees from users. If you trade, they have fees, and the more active trading you do, the more income for the exchange.
They don't care that you will be taxed or not, it's your personal issue with government. Exchanges only care that your coins are tainted or not, whether your coins are from mixers or not because they have to obey AML and they don't want to receive tainted coins.
I have a second account at Binance. I had 100 coins I was trying to move over to Coinbase, but got an error saying that you need 400 of these coins to be-able to move them.
You can check Binance's page on Trading fee, Deposit and Withdrawal information like Min Deposit, Min Withdrawal and Withdrawal fee.
https://www.binance.com/en/fee/cryptoFee