How to publish in the extranet / web extra fees for early /late check in or check out

Check out for my appartment is between 9 and 11 am.

Somebody must take back the keys and return the deposit to the customer.

Today the customer told me that he is going to leave at 3 am . WE discussed about the extra cost it suppose

I dont want to have this discussions in the future , so i want to publish in The extranet/web the price of this extraservice in advance,

I can’t find any place to publish this condition