Can I see how much business I send to each supplier so I can ask them for better commission?

Yes, you can see how much business you are putting through each supplier, as long as those bookings pass through your system. Reporting will normally let you group your sales by supplier, so you can see how many bookings went to each airline, hotel supplier, consolidator or land operator over a period you choose, and what those bookings were worth. That is exactly the information you want in front of you before you ask anyone to improve your terms.

The picture is only as complete as what you record. Anything booked through a connected supplier is counted on its own, because the system already knows where the booking went. Bookings your staff take by phone or by email with a supplier you are not connected to will only show up if someone enters them, so if a good part of your business is still handled that way, the report will understate those suppliers until that habit changes.

How much detail you get depends on the supplier and on your plan. Volume and value are usually straightforward. Commission is only as accurate as what you have recorded against each booking, and some suppliers do not send back a clean breakdown through their API, so you may still need to check the report against their own statements. Cancellations and refunds also have to be treated properly, or a supplier can look stronger than it really was.

Before you go into the conversation, check which of your suppliers are actually connected, make sure your offline bookings are being entered by your staff, and run the report over a long period rather than a quiet month so the numbers hold up when the supplier questions them.