Can I stop certain hotels from appearing on my portal?

Yes. Most setups let you keep a list of hotels you do not want to sell, and anything on that list is removed from the search results before your customer ever sees it. Agencies use this for properties they have had complaints about, for hotels in areas they would rather not send guests to, and sometimes for properties they already sell directly and do not want showing at a supplier price alongside their own.

You can usually work the other way round too. If you want your portal to show only a chosen set of properties, for a corporate client with an approved hotel list or for a destination you specialise in, you can keep an allowed list instead of a blocked one, and everything outside it stays hidden.

There are two honest limits. The first is that a hotel can reach you through more than one supplier, and the details each supplier sends are not always identical, so blocking a property once does not always remove every copy of it. The second is that the amount of control you get depends on your plan and on how the connection to each supplier is set up, so check what your own setup allows rather than assuming it is unlimited.

The simplest way to be sure is to block one property, then search that same city on your portal as a customer would and confirm it has really gone from the results before you rely on the list.