If I buy from a supplier in one currency and sell to my customer in another, will the system keep track of both?
Yes, a booking can hold one currency on the buying side and another on the selling side, so your back office is not left doing that sum by hand.
When a booking is made, the supplier cost is stored in the currency the supplier actually charged you in, and the price your customer pays is stored in the currency you sell in. The system converts between the two using a rate you set, and it keeps that rate against the booking. That matters, because a rate that moves next week should not quietly change what last week's booking looks like in your reports. Your invoice and voucher go out in your selling currency, while your cost reports and your supplier reconciliation stay in the currency you will actually be billed in.
Be honest with yourself about where the gap sits. The rate you use is the rate you chose, and it will rarely match the exact rate your bank or your card processor applies on the day the money moves. That small difference is a real cost, and it shows up when you settle with the supplier rather than at the time of booking. Some agencies load a small buffer into their conversion rate to cover it. Which currencies you can sell in also depends on what your payment gateway and your suppliers support, so the software is only one half of the answer.
Before you switch on a second selling currency, check with your payment provider which currencies they can actually collect and settle in, and decide who inside your business will be responsible for keeping the conversion rate up to date.
