Section 61.16 - Base documents(a) The Base Document is a complete tariff which incorporates all effective revisions, as of the last day of the preceding month. The Base Document should be submitted with a cover letter as specified in § 61.15(i) and identified as the Monthly Updated Base Document.(b) If there have been revisions that became effective up to and including the last day of the preceding month, a new Base Document must be submitted within the first five business days of the current month that will incorporate those revisions. 76 FR 43211 , July 20, 2011