200 F.3d 867 (D.C. Cir. 2000)
Anadarko Petroleum Corporation, et al.,Petitionersv.Federal Energy Regulatory Commission, RespondentAmoco Production Company, et al., Intervenors
Nos. 98-1227, 98-1232, 98-1297 & 98-1298
United States Court of AppealsFOR THE DISTRICT OF COLUMBIA CIRCUIT
Filed January 21, 2000

On Petition for Rehearing
Before:  Edwards, Chief Judge, Sentelle and Randolph,  Circuit Judges.
Opinion for the Court filed Per Curiam.

Per Curiam:

1
Subsequent to our decision of October 29,  1999, the Commission petitioned for rehearing seeking clarification on the issue of the effective date for refunds discussed  in Part V of our opinion.  See Anadarko Petroleum Corp. v.  FERC, 196 F.3d 1264, 1269-70 (D.C. Cir. 1999).  Information  presented to the Commission in other proceedings indicated  that two of the factual assumptions upon which our opinion  was premised were incorrect.  First, contrary to this panel's  understanding, see id. at 1270, the tax assessment sent to the  producers by the State of Kansas betweenOctober and  November of a given year was for the same calendar year and  not the previous year.  Second, the Commission discovered  that producers most commonly sought reimbursement of the  Kansas ad valorem tax from their customers in lump sum  transactions and not by "raising their prices in individual  transactions."  Id.  Thus, the Commission was uncertain how  to give effect to the court's holding that "it is the overcharges  made in those individual transactions (plus interest) that the  producers must now repay."  Id.


2
Whatever the nature of these transactions, the principle  embodied in our decision remains unchanged.  The Kansas  tax should not have been subject to reimbursement for sales  exceeding the maximum lawful price under    110 of the  Natural Gas Policy Act of 1978, 15 U.S.C.    320(a)(1) (1988)  (repealed).  However, the producers did not have notice that  this practice was questionable until October 4, 1983.  See  Anadarko, 196 F.3d at 1266 (describing our earlier holding in  Public Service Co. of Colorado v. FERC, 91 F.3d 1478, 1490  (D.C. Cir. 1996)).  If the producers collected tax reimbursements from their customers after that date, whether by lump sum transactions or by any other means, they did so unlawfully and must refund the amounts collected with interest,  provided that the tax reimbursements caused their sales to  exceed the maximum lawful price.  We leave to the Commission the unenviable task of applying this principle to the facts  of ancient transactions.


3
The petition for rehearing is granted.  The portions of our  opinion of October 29, 1999, which are inconsistent with this  opinion are withdrawn.  The orders under review are vacated  insofar as the question of refund dates is concerned and this  issue is remanded to the Commission for further proceedings  consistent with this clarification.

