For me, I run in this with service contracts, but it could be anywhere you use a billing plan. The idea is that you charge an annual price. Say $12,000 for the year, and you want the billing plan to spread this evenly across periods. (say $1000/month or $3000/quarter).
The first thing that needs to happen is to update the pricing condition type.
Update the calculation type to be M for monthly or N for annual.
Now, if you choose annual, please be aware that the calculation is performed by days, not by months. So if you bill monthly, the amount for Jan will be greater than Feb because of the difference in days per month.
SAP does provide OSS note: 92655 as a work around for this.
Thanks for reading,
As always, thanks for reading and don't forget to check out our SAP Service Management Products at my other company JaveLLin Solutions,Mike