common_fate

You mentioned in your question that it is a two year award... Now if that means it was a multi-year award for professional services and it happens that the services are severable AND you plan to incrementally fund the fixed price award.... It's possible that you may require a breakdown to ensure that when crossing fiscal years you have adequate information for your funding profile. See 41 USC §3904. Contract authority for severable services contracts and multiyear contracts for descriptions of all the different types of services that could fall into this category.

My experience was different. I regularly saw multiple CLINs referenced in Block A. I never even considered the issue of identifying which CLIN in Block A to be about billing. It was far more important to ensure the correct distro statement/ instructions for preparation was applied to the particular data being procured. As it relates to your original question, the monthly status report should be its own deliverable with its own CDRL. Reference all applicable CLINs in Block A (for example: 0001 -0002 (0003 if exercised)) ... but not because of the billing question, but because the monthly status report would have its own distro statement and instructions for preparation versus the other CDRLS on the award.