72 Pa. Stat. § 2283
Every insurer transacting such marine insurance in this Commonwealth shall file, on or before the first day of June in each year, with the Department of Revenue, and in the form prescribed by it, a report of all the items pertaining to its insurance business as enumerated and prescribed in the preceding section of this act. Every insurer, which has been writing such insurance in this Commonwealth for three years, shall furnish to the Department of Revenue a statement of all of the aforementioned items, in the form prescribed by it, for each of the preceding three calendar years. An insurer which has not been writing such marine insurance for three years shall furnish to the Department of Revenue a statement of all the aforementioned items for each of the calendar years during which it has written marine insurance. Every insurer, at the time of making the reports required by this section, shall compute and pay into the State Treasury, through the Department of Revenue, the tax, if any, then due the Commonwealth.
If the insurer has transacted such marine insurance for three years, it shall (1) ascertain the average annual underwriting profit as defined by this section, derived from its aforesaid marine insurance business written within the United States during the last preceding three calendar years; (2) ascertain the proportion which the average annual premiums of the insurer from such marine insurance, written by it in this Commonwealth during the last preceding three calendar years, bears to the average total marine premiums of the insurer during the same three years; (3) compute an amount of five per centum on this proportion of the aforementioned average annual underwriting profit from such marine insurance; and (4) charge the amount of tax thus computed as a tax upon the marine insurance written by it in this Commonwealth during the current calendar year. The insurer shall, each year, compute the tax, according to the method described in this section, upon its average annual underwriting profit from such marine insurance during the preceding three years, including the current calendar year, namely, at the expiration of each current calendar year; the profit or loss on the marine insurance business of that year is to be added or deducted and the profit or loss upon such marine insurance business of the first calendar year of the preceding three-year period is to be dropped, so that the computation of underwriting profit, for purposes of taxation under this act will always be on a three-year average: Provided, however, That an insurer which has not been writing marine insurance in this Commonwealth for the three years shall, until it has transacted such business in this Commonwealth for that number of years, be taxed on the basis of its annual underwriting profit on marine insurance written within the United States for the current calendar year, subject however to an adjustment in the tax as soon as in accordance with the provisions of this section, it is enabled to compute the tax on the aforementioned three-year basis: And provided further, That in the case of mutual companies there shall not be included in underwriting profit, when computing the tax prescribed by this section, the amounts refunded by such companies on account of premiums previously paid by its policyholders.
In making assessments under the retaliatory provisions of section two hundred and twelve of the act, approved the seventeenth day of May, one thousand nine hundred and twenty-one (Pamphlet Laws, seven hundred eighty-nine), known as "The Insurance Department Act of one thousand nine hundred and twenty-one," credit shall be allowed for any taxes paid or payable under this section.
72 P.S. § 2283