Boylston Market Association (Boylston) (plaintiff) is in the business of managing real estate. Boylston periodically purchases prepaid insurance policies covering three or more years for its properties. Rather than deduct the entire cost of insurance in the year of purchase, Boylston prorates the prepaid premium and each year deducts only the amount allocable to that year. Prior to 1936, Boylston purchased prepaid insurance in the amount of $6,690.75. In 1936, it paid another $1,082.77 for insurance. Boylston calculated that a total of $4,421.76 was allocable to 1936 and accordingly deducted that amount as insurance premiums paid in 1936. Prior to 1938, Boylston purchased prepaid insurance in the amount of $6,148.42 and paid an additional $890.47 during 1938. Boylston calculated that a total of $3,284.25 was allocable to 1938 and deducted that amount accordingly. The Commissioner (defendant) disallowed the amount of deductions taken by Boylston. The Commissioner determined that Boylston was only entitled to deduct $1,082.77 in 1936 and $890.47 in 1938, the amounts actually paid in 1936 and 1938.