I wanted to let other hosts know about the confused way air BnB software handles base rates and custom rates, and their support people do not understand it.
What happened to me:
We decided to change the minimum number of people in a booking. Previous rate $150 for first two people and extra $30 each for third and subsequent guests. New rate $180 for the first three guests and extra $30 for fourth and subsequent guests.
I changed the base rate and number of guests but I noticed that the calendar still displayed $150 which was the old rate. After five days of multiple messages back and forth to various different people at customer support who didn't understand what had happened, someone eventually told me that there was a custom rate for exactly the same as the previous base rate on all the open days on my calendar. During the five days I got another booking for two nights and the guest was charged $60 too low. I then had another long dispute with Air BnB - I asked Air BnB to make up the $60 deficit because they had advertised the wrong rate and continued to advertise it for five days after I noticed and informed them. (Eventually, reluctantly they paid me the $60.) I refused to ask the guest for $60 because they had paid the advertised price.
I have worked out what the software does:
There is no such thing as a base rate. When you open days on the calendar the "base rate" is automatically converted to a "custom rate" for those open days.
Suggested steps if you change your base rate for any reason:
Close all the unbooked days on your calendar. Change the base rate. Open up the calendar again.
Something else I have learned:
Air BnB is happy to take our money but they do not employ customer support people who understand the software interface and they are very reluctant to pay a deficit due to their mistake.