how to active document split after go-live

Dear all,

We went-live in Jun. 2009, now we woule like to active document splitting .

After document splitting function is actived, user always got an error message 'GLT0 002 Document splitting: Items for clearing &1/&2/&3/&4 not found' when they clear the customer/vendor open items. My question is does SAP allow active this function after system go-live? or must implement migration project?

Thanks,

Ben