Can I add a note to a hotel booking asking for a late check in or a twin bed?

Yes, in most cases you can send a special request with a hotel booking, but please treat it as a request and not something that is confirmed. The note travels with the reservation to the hotel, and the hotel decides on the day whether it can be honoured, usually depending on how full they are when your guest arrives.

On the booking screen your staff can type a short request in plain English, such as a late arrival, a quiet room, a twin bed instead of a double, a high floor or a honeymoon stay. Where a supplier supports it, common requests can also be sent as standard options rather than free text, which travels better because nothing has to be read or translated by the hotel. Keep the wording short and simple, because a long paragraph is more likely to be cut off or ignored.

There are real limits worth knowing. Not every hotel supplier accepts a request field, and some accept one only on certain rate types, so the box may not appear for every result. Anything that costs money or changes what you have actually bought is not a special request. An extra bed, a cot, a different room category or a confirmed early check in has to be booked as the correct room and rate, or arranged with the hotel directly and paid locally.

It is worth checking which of your connected suppliers pass requests through, and adding a line to your voucher telling the guest that requests are subject to availability on arrival, so nobody turns up expecting a guarantee.