I concur in the majority opinion. I write separately to offer these additional reflections on the “as applied” challenge to the fee as a tax.
A charge that is labeled a regulatory fee may indeed be a tax in disguise if “the amount of fees assessed and paid exceeded the reasonable cost of providing the [regulatory] services for which the fees were charged, or [if] the fees were levied for unrelated revenue purposes.” (Sinclair Paint Co. v. State Bd. of Equalization (1997) 15 Cal.4th 866, 881 [64 Cal.Rptr.2d 447, 937 P.2d 1350].) Here, there is no allegation that the fees in question are being used for unrelated revenue purposes. Rather, it is contended that only 40 percent of water rights holders are being charged a fee that by right should be charged to all water rights holders, and therefore the fee is not sufficiently linked to the regulatory costs generated by those on whom the fee is imposed and constitutes a tax.
Every government entity that imposes a regulatory fee must decide who should be subject to the fee and who should not. A number of factors may go into that decision, including assessments of the regulatory burdens imposed by the various actors and the administrative convenience of imposing the fee. As the majority states: “ ‘Legislators “need only apply sound judgment and consider ‘probabilities according to the best honest viewpoint of informed officials’ in determining the amount of the regulatory fee.” [Citation.]’ ” (Maj. opn., ante, at p. 438.) So, too, legislators and regulators need only make reasonable decisions about who should be subject to a regulatory fee.
In the present case, the State Water Resources Control Board claims that “some 95 percent of its time and expense are directed toward servicing and regulating those licensees and permittees against whom the challenged fees were assessed.” (Maj. opn., ante, at p. 441.) The support for this contention *448stems primarily from a document produced by the board on April 15, 2004, shortly after the present litigation commenced. Because of the uncertain reliability of this document, as well as the trial court’s lack of findings, remand is appropriate to determine whether the board’s decisions regarding who would be subject to the fee were reasonable.
Werdegar, J., concurred.
The petition of both appellants and respondent for a rehearing was denied April 20, 2011, and the opinion was modified to read as printed above. Cantil-Sakauye, C. J., did not participate therein.