Generating BS Elements from Budget and Posting Data 
Use
You use this function if you previously carried out budgeting in BCS without a budget structure and now want to begin using a budget structure.
There are programs available for this purpose which:
generate budget addresses based on existing budget data in the FM area/fiscal year
generate posting addresses based on existing actual/commitment data in a FM area/fiscal year
Activities
You execute these programs in Customizing of Funds Management under
Master Data
Use of Account Assignment Elements
Budget Structure (BCS)
Generate Budget Addresses from Budget Data 
or
Generate Posting Addresses from Actual Data
.
See the program documentation for more information.