Will my portal show the last date a hotel can be cancelled without a charge?

Yes, in nearly every case the cancellation deadline is shown before your customer pays. Each rate that comes back from a supplier carries its own cancellation terms, and those terms are displayed on the room and again on the review page, so the customer can see whether the rate is refundable and, if it is, the date and often the local time after which a charge applies. The same terms are repeated on the confirmation and the voucher, so your customer has them in writing.

The deadline is set by the hotel, not by you or by your portal, so it varies a great deal. Some rooms can be cancelled up to the day of arrival, others need several days or even weeks of notice, and non refundable rates cannot be cancelled at all without losing the money. Peak dates, long stays and group bookings often carry stricter terms than the same room on a quiet week, so the answer for one booking is not the answer for the next.

One point worth knowing is that the deadline runs in the hotel's own local time zone, not your customer's. A booking that looks like it still has a day left can already be past its deadline if the hotel is several hours ahead. When a cancellation is close to the line, treat the hotel's clock as the one that counts.

When you are checking a rate, read the cancellation line on the room before you quote it to your customer, because two rooms in the same hotel at a similar price can have very different terms.