N.Y. PBS Law § 118

§ 118. Payment to an authorized payment agency. 1. In any case where a\npublic utility company or municipality rendering equivalent utility\nservices permits its customers to pay their bills to a payment agency\nauthorized by the corporation or the municipality for collection of\nbills, the date of payment to such authorized payment agency shall be\nthe effective date of payment of such bill, and the payment shall be\nregarded as if it were paid directly to the corporation or municipality\non such date. Where a customer of such corporation or municipality has\npaid a bill to an authorized payment agency on or before a designated\ndue date, no penalty or extra charge shall accrue on such bill for the\nreason that the payment did not reach the corporation or municipality on\nor before the designated due date. Notwithstanding the provision of this\nsection, payments to authorized payment agencies by residential\ncustomers shall be governed by article two of this chapter.\n 2. Backbilling. Except as provided for residential utility service\npursuant to article two of this chapter, no public utility company or\nmunicipality may render a bill for previously unbilled service, or\nadjust upward a bill previously rendered, to a residential customer\nafter the expiration of twenty-four months from the time service to\nwhich the bill or adjustment pertains was provided. This provision shall\nnot apply when the culpable conduct of a customer caused or contributed\nto the failure of the company or municipality to have rendered timely or\naccurate billing.\n 3. Credit or refund of overpayments. (a) The commission shall have the\npower to require a public utility company or municipality to provide a\nrefund or credit to a customer when a payment has been made in excess of\nthe correct charge for actural service rendered to the customer.\n (b) If a residential customer becomes eligible for a lower rate\nbecause he or she changes the character of the service received and if\nexcess payment resulted from the failure of the customer to notify the\nutility or municipality providing service of a change in the character\nof service received or from the failure of the utility or municipality\nto change the rate after such notification by the customer, such a\ncustomer will be entitled to such lower rate from the date the change\noccurs but such a customer shall not be entitled to such lower rate for\nmore than twenty-four months prior to the giving of actual notice to the\nutility or municipality providing service.\n