Statements A through M, O, P, and supporting schedules, in § 154.312 and § 154.313, must be based upon a test period.

If the natural gas company has been in operation for 12 months on the filing date, then the test period consists of a base period followed by an adjustment period.

The base period consists of 12 consecutive months of the most recently available actual experience. The last day of the base period may not be more than 4 months prior to the filing date.

The adjustment period is a period of up to 9 months immediately following the base period.

The test period may not extend more than 9 months beyond the filing date.

The rate factors (volumes, costs, and billing determinants) established during the base period may be adjusted for changes in revenues and costs which are known and measurable with reasonable accuracy at the time of the filing and which will become effective within the adjustment period. The base period factors must be adjusted to eliminate nonrecurring items. The company may adjust its base period factors to normalize items eliminated as nonrecurring.

If the natural gas company has not been in operation for 12 months on the filing date, then the test period must consist of 12 consecutive months ending not more than one year after the filing date. Rate factors may be adjusted as in paragraph (a)(4) of this section but must not be adjusted for occurrences anticipated after the 12-month period.

Adjustments to base period experience, or to estimates where 12 months' experience is not available, may include the costs for facilities for which either a permanent or temporary certificate has been granted, provided such facilities will be in service within the test period; or a certificate application is pending. The filing must identify facilities, related costs and the docket number of each such outstanding certificate. Subject to paragraph (c)(2) of this section, adjustments to base period experience, or to estimates where 12 months' experience is not available, may include any amounts for facilities that require a certificate of public convenience and necessity, where a certificate has not been issued by the filing date but is expected to be issued before the end of the test period. Adjustments to base period may include costs for facilities that do not require a certificate and are in service by the end of the test period.

When a pipeline files a motion to place the rates into effect, the filing must be revised to exclude the costs associated with any facilities that will not be in service as of the end of the test period, or for which certificate authorization is required but will not be granted as of the end of the test period. At the end of the test period, the pipeline must remove from its rates costs associated with any facility that is not in service or for which certificate authority is required but has not been granted.

The Commission may allow reasonable deviation from the prescribed test period.