Exchange commission explained

Exchange commission is the fee a betting exchange charges on your winnings. Here's how it works on a back bet, a lay bet and a trade, and how to compare rates.
Instead of building a margin into the odds, an exchange takes a percentage of your net profit in each market. There's no charge on your stake, and nothing to pay if you're behind in that market. One major exchange charges up to five per cent as standard in the UK, and several others advertise two. Rates change, so check the current terms.
Say you back a team for twenty pounds at three, and it wins. That's forty pounds profit. Five per cent commission takes two pounds, so you keep thirty-eight. So three at five per cent pays the same as two point nine at a bookmaker. At two per cent, it's worth two point nine six. The gap grows with the odds.
When you lay, you're the bookmaker. Lay a twenty pound stake at three and your liability is forty pounds. If the team doesn't win, you collect twenty pounds, less five per cent, so nineteen.
On a trade, back twenty pounds at three and lay twenty-four at two point five. That locks in four pounds either way. You pay five per cent just once, twenty pence, and keep three pounds eighty.
That looks small, but scalpers make hundreds of trades, so commission adds up. Always record your profit after commission, because a method that works before it can fail after it. Please bet responsibly.