Proforma Invoice in Intracompany STO Process

Hi Gurus,

I am trying to make Proforma Invoice in STO Intra company. But it is giving the errror "Not relevant for billing". Actually i want to create a excise Invoice from this Pro forma Invoice. I have also maintained NLN item category in Copy control between NL to F8. but still the invoice is not created. Can anybodu plz tell me where i am missing the configuration?