1. In Accounts Payable, Configuration, click Posting information
  2. Select Line Items or Receipts
  3. Select Purchase order number in the appropriate position under Field Name and enter a length for the purchase order number
 

Note: Changes to the journal reference apply to transactions posted after the change was made. The changes are not retroactive to all posted transactions.

For more information, refer to How to define journal reference fields in The Financial Edge (BB63279)