Will Rates changes affect all reservations?

Q: If I change my rates through Rates Setup, is that going to affect all of my old reservations that used those rates?

Once a rate is "used" or "added" to a reservation, it just adds the transactions as indicated in the rate without any relation back to the rate definition.  So changing rates will not affect any previous transactions, nor will historical reports be affected.  You could even delete old rates and add new ones.

However, if you change rates that could still be applied to current reservations (e.g. long-term stays), then if you go back and "auto-calculate" again, it would apply the new rates (and appropriate credits for the old transactions).  So if you're changing rates for a new year, it's best to make a copy the rates and include the appropriate dates in "Season Dates Applicable" for each rate.  That way it will always know the proper rate to apply for any given time period, whether it's an old reservation or a new one.