Can my travel agency software store my customers' passport details and warn me when a passport is about to expire?

Yes. Most travel agency software keeps a profile for each customer where you can save the details you need again and again, including the passport number, the name exactly as it is printed, the nationality and the expiry date, so your staff are not asking the same traveller for the same information before every trip.

The warning part depends on the system you use. Many will put a flag on the profile or send your team a reminder when a passport is getting close to running out, which matters because a lot of countries want the passport to stay valid for several months beyond the travel date. Whether that reminder reaches you on its own, or whether somebody has to run a report and look, varies by provider and sometimes by the plan you are on, so please ask before you start relying on it.

Passport information needs care. Give it only to the staff who genuinely need it, keep their access levels tight, and clear out details you no longer have a reason to hold. The privacy rules in your own country decide how long you may keep this information and what you must tell the traveller about it, and that responsibility sits with you as the agency rather than with the software.

Ask your provider whether passport expiry alerts are included and how far ahead they arrive, then open a few of your existing customer profiles and check that the expiry dates are actually filled in, because a reminder can only work on information somebody has entered.