(b) Definitions. -- For purposes of this section, the term:

1. (1) "Eligible taxpayer" means a utility which has provided telephone service to qualified low-income residential customers at special reduced rates.
2. (2) "Cost of providing telephone service at special reduced rates" means the amount certified by the Public Service Commission under the provisions of section two, article two-c, chapter twenty-four of this code, as the revenue deficiency incurred by a telephone utility in providing telephone service at special reduced rates, as required by section one, article two-c, chapter twenty-four of this code.
3. (3) "Special reduced rates" means the rates ordered by the Public Service Commission under the authority of section one, article two-c, chapter twenty-four of this code.
4. (4) "Qualified low-income residential customers" means customers eligible to receive telephone service at special reduced rates.

(d) When credit may be taken. -- An eligible taxpayer may claim a credit allowed under this section on its annual return for the taxable year for which it receives certification of the amount of its revenue deficiency from the Public Service Commission.

Notwithstanding the provisions of section sixteen of this article to the contrary, no credit may be claimed on any declaration of estimated tax filed for such taxable year prior to July 1, of such taxable year. Such credit may be claimed on a declaration or amended declaration filed on or after such date, but only if the amount certified will not be recovered by application of the tax credit allowed by article thirteen-g of this chapter. In such event, only that amount not recovered by the tax credit allowed by article thirteen-g of this chapter may be considered or taken as a credit when estimating the tax due under this article. In no event may the eligible taxpayer recover more than one hundred percent of its revenue deficiency as certified by the Public Service Commission.