Recurrences
In the you can define the contract lines billing frequency. There are six types of recurrences:
- Daily - items are billed every 
ndays or everynweekdays. - Weekly - items are billed every 
nweeks and on a particular day of the week. - Monthly - items are billed every 
nmonths on a particular day. - Yearly - items are billed annually on a particular day of a particular month (for example, every August 30th) or on a specific day of the week in a month (for example, every last Friday in March).
 - Once - a contract line is billed once and applies to a moment in time.
 - Custom - items are billed on a custom basis. A series of billing dates can be specified. An invoice is generated to cover each date.