Margin Trading is a strategy of trading crypto assets that involves borrowing funds and allows traders to leverage their positions with higher funds than they have.
On Bitfinex, Profit/Loss (P/L) in Margin Trading is always settled in the last symbol of a pair.
If you open a BTC/USD long position, you buy Bitcoin (BTC) using Margin Funding US Dollars (USD), and if the price rises, you sell the BTC and the realised profit/loss, which equals [amount] * ([sell price] - [buy price]), is yours to keep (or to pay if you realise a loss).
When you open a BTC/USD short position, you sell BTC (your own BTC + Margin Funding BTC) and then repurchase them when the price falls to close the trade. You will keep [Amount] * ([buy price] - [sell price]), which will be in USD (or to pay if you realise a loss). This is again in USD, as you will have some USD left over to buy back the BTC that you previously sold at a higher price.
If you only wish to keep BTC after closing a Margin trade, you must manually convert your USD earnings into BTC using the BTC/USD pair by selecting Exchange in the Order Form box on the Trading page.
Note: Bitfinex also offers a feature to claim your position, which allows the use of funds you have in your Margin Wallet to settle a leveraged position as an exchange buy or sell. You can learn more about how to claim your position here.
If you have any questions, please feel free to reach out to Bitfinex Support. We are happy to help!