Preinstallation Accuracy. If a meter is tested under Regulation .03B and G of this chapter, an owner may not install or return to service a meter that is more than 0.5 percent fast or more than 1.5 percent slow. In-Service Performance Test Accuracy. If a meter is tested under Regulation .03E of this chapter, an owner shall count the test as a failure if the meter and associated metering device, if installed, are found to be more than 2 percent fast or slow. Balance. If a meter's accuracy at check flow is found to differ from accuracy at full rated flow by more than 1 percent, an owner shall adjust or repair, or both, and test the meter before returning it to service. Billing Adjustment Fast Meters. Bill Recalculation. If an accuracy test shows an over-registration of more than 2 percent at check flow, the owner shall recalculate the bills for service of the last customer of record receiving service through the meter and shall make a refund if the amount of the adjustment exceeds $10. The refund shall be for the period that the customer received service through the meter, but for not more than the periods established in §D(1)(b) and (c) of this regulation. Known Date of Error. If the date on which the error first developed or occurred can be established, then the owner shall make a refund based on that known date. Unknown Date of Error. If the known date of error cannot be established, then it shall be assumed that the over-registration existed for a period of 3 years or a period equal to 1/2 of the time since the meter was last tested, whichever is less. Slow Meters. If an accuracy test shows an under-registration of more than 2 percent at check flow, the owner may bill the customer 1/2 of the unbilled undercharge for a period of 12 months, unless the meter has been tested within that 12-month period, in which event the utility may bill the customer 1/2 the unbilled undercharge for the period since the meter was last tested. If the amount of under-registration is less than $20, the utility may not bill the customer for the undercharge. Nonregistering Meters. If a meter is found not to register, the owner may issue an estimated bill. If the customer is informed of the nonregistering meter in less than 4 months of the meter becoming nonregistering, the utility may bill the customer for estimated consumption for the duration of the nonregistration. If the customer is not informed of the nonregistering meter in less than 4 months of the meter becoming nonregistering, the utility may bill the customer for 1/2 of the estimated consumption for the duration of the nonregistration up to a maximum of 6 months.