In determining the amount of taxes to be assessed under the provisions of sections 8551 and 8552 of this title, there shall be deducted from the full amount of such premiums and assessments all sums paid for return premiums on cancelled policies upon risk located in this State and dividends actually paid or allowed to policyholders residing therein. Nothing in this section shall be construed to allow dividends in scrip, in stock, mutual or mixed companies, or surrender values for life policies, to be considered return premiums.