How is the NIH Contract Access Fee (NCAF) paid on labor hour awards?

Question: 
How is the NIH Contract Access Fee (NCAF) paid on labor hour awards?

The NCAF is paid on each obligated amount based on the funding document. If a labor hour order is incrementally funded, the corresponding fee is based on the incremental funding and not the ceiling. The contractor includes the entire fee (based on the funding of the order) on the first invoice.