Will my customer be able to see the markup I have added on top of the supplier price?

No, the customer sees one single price, not your cost and your markup sitting side by side. When a search comes back from the supplier, the system adds your markup quietly in the background and shows only the final selling price on the results page, the booking page and the voucher. Your margin stays inside your own admin panel, where you and the staff you allow can see the supplier cost, the markup applied and what is left for you.

The one thing to watch is the paperwork that comes from the supplier rather than from you. A hotel voucher, an airline ticket or a confirmation email sent directly by the supplier may carry their own reference and sometimes their own rate, and that is outside your control. This is why most agencies use their own branded voucher and invoice from the portal and do not forward the raw supplier document to the traveller.

How much you can hide also depends on the product. On a normal prepaid booking the customer only ever deals with your price. On a pay at hotel rate, the property collects the money itself, so the traveller will see the hotel's rate at the counter and your markup has to be handled as a separate service fee instead.

Before you go live, do a test booking on each product you sell and read every document the traveller receives end to end, so you know exactly what price reaches them and from whom.