California Code, Streets and Highways Code - SHC § 36745

(a) Upon the disestablishment of a district, any remaining revenues, after all outstanding debts are paid, derived from the levy of assessments, or derived from the sale of assets acquired with the revenues, or from bond reserve or construction funds, shall be refunded to the owners of the property or businesses then located and operating within the district in which assessments were levied by applying the same method and basis that was used to calculate the assessments levied in the fiscal year in which the district is disestablished.  All outstanding assessment revenue collected after disestablishment shall be spent on improvements and activities specified in the management district plan.

(b) If the disestablishment occurs before an assessment is levied for the fiscal year, the method and basis that was used to calculate the assessments levied in the immediate prior fiscal year shall be used to calculate the amount of any refund.