47 CFR § 65.701
Period of review
February 16, 2021
For both exchange and interexchange carriers subject to this part, interstate earnings shall be measured over a two year period to determine compliance with the maximum allowable rate of return. The review periods shall commence on January 1 in odd-numbered years and shall end on December 31 in even-numbered years.
[60 FR 28546, June 1, 1995]