You will be required to define, for each of the controlling areas, the ‘Number Ranges’ for all transactions that will generate documents in CO. Once done for a controlling area, you may copy from one controlling area to other controlling areas when you have more than one such area.
To avoid too many documents, SAP recommends grouping multiple but similar transactions, and then assigning number ranges to this group. Further, you may create different number ranges for plan and actual data. As in FI, the number ranges can be internal or external. The document number ranges in CO are independent of fiscal years.