Can I give my customers a discount code to use on my portal?

Yes, on most plans you can set up a discount code and let your customers type it in before they pay.

A code is normally made in your admin area, where you decide what it takes off, whether it is a set amount or a share of the booking value, and when it starts and stops working. You can usually limit it as well, so it only applies to hotels and not flights, or only to bookings above a certain value, or only for a single use per customer. When the customer enters the code at the payment step, the portal checks it, shows the reduced amount and records against the booking which code was used, so you can see later how a campaign performed.

It is worth being clear about who pays for the discount. The code comes off your own margin, not off what the supplier charges you, so if you have already added a small markup and then offer a large code on top of it, you can end up selling below your cost. The portal will not stop you doing that, so it is on you to set the code within what your markup can carry. Some payment methods and some supplier rates also sit outside discounting, so a code may not apply to every product on your portal.

Before you promote a code, make one with a short validity, run a test booking through with it, and check that the amount taken and the amount recorded on the booking are both what you expected.