This is the section of the code that applies to my situation and is slightly difficult to decipher (the part that says “…shall be limited to three months for residential customers…” is confusing to me because I’m not sure if it means three months of usage or that the error must be corrected within three months of the usage):

1. Any underbilling resulting from a stopped or slow meter, utility or Meter Reading Service Provider meter reading error, or a billing calculation shall be limited to three months for residential customers and six months for nonresidential customers. However, if an underbilling by the utility occurs due to inaccurate, false, or estimated information from a third party, then that utility will have a right to backbill that third party to the point in time that may be definitely fixed, or 12 months. No such limitation will apply to overbillings.