Each insurer that has a tax liability during the prior calendar year of $50,000 or more must file an installment payment by the 15th of each month, March through August, of the current year equal to 15% of the prior calendar year tax liability. ARS § 20-224(E).
Completing Form E-INSTALL is optional. It does not need to be included with your OPTins filing.
Insurers MUST use the NAIC OPTins system to pay Arizona tax installments. ARS § 20-224(K).