John K

You will have to contact booking.com customer service team to resolve this issue. IF you log into your property extranet on Booking.com, click on the "Inbox" tab at the top of the page and then click 'Booking.com Messages" there you will see the customer service contact phone number on the right hand side of the page under "Other questions - contact your support team."

Im assumming its just a it problem you having, but customer service team will definitely be able to help you.

If theres no rate differences in the change in the number of guests, i guess it would not be important to change or notify booking.com.

But if there is a rate difference, i would update by reconciling the booking on Booking.com extranet, by logging on to your property extranet and on the home page you will be arrivals, departures and stay overs. if you click on the guests booking/name their page will come up and on the right hand side, you can change the reservation date and/or price. Click the tab and following accordingly, therefore you will only be commissioned the new price you have submitted.

Self check in would be the most preferred option. But if you choose to charge the guests an extra fee for late self check in's may result with some negative reviews, which is unfair as the check in hours are clearly stated. But from my experience, inform Booking.com customer service or leave a message with the guests via Booking.com a self checkin is arranged with any other details.