SAP Functional, Basis and ABAP Programming Reference Books
Billing Block will not worked if you did not assign it

Define the possible block indicators in SM30 - V_TVFS 

and 

allocate them to the billing types concerned in SM30 - V_TVFSP.
 

Your Billing Block will not worked if you did not assigned it to the desired billing types.
 

You can auto block by :- 

1.  sales document type in transaction VOV8, fields Billing Block,

or

2.  item categories in SM30 - V_TVAP, by filling the fields Billing Block.
 

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