Will my customers know about taxes and fees they have to pay at the hotel instead of to me?

Yes, in most cases, as long as the supplier sends that information through. Hotel rates often separate what the customer pays you at the time of booking from what they have to settle at the property itself, such as city tax, a tourism levy or a resort fee. When a supplier passes those amounts across the API, your portal can show them on the room result, again on the checkout page and on the confirmation, so the customer understands the room is paid for but there is still something to hand over at reception.

The honest limit is that this depends entirely on what each supplier chooses to send. Some return a clear breakdown of every mandatory charge payable at the hotel. Others only mention it in the rate description as free text, and a few say nothing at all, usually because the tax is collected locally and varies from one city or even one property to the next. Where the supplier sends no data, your website cannot invent it, so your staff may still get the occasional question from a customer who was surprised at check in.

What you can control is how it is presented. You can choose whether these charges sit next to the room price or lower down with the cancellation terms, and you can add your own standing wording to your vouchers and emails reminding customers that local taxes may be payable directly to the hotel. That one line of wording prevents most of the complaints agencies get on this.

It is worth checking which of your hotel suppliers return a proper fee breakdown, then setting your voucher wording to cover the ones that do not.