Per annum refers to a duration of one year, or on a yearly basis. The term is commonly used in regard to a sum due at intervals of one year or over the course of a year. Several examples of how the term is used are:
The per annum cost to maintain a car is $4,000; thus, a vehicle owner can be expected to pay out a total of $4,000 in maintenance costs for his automobile over a one-year period.
The per annum gross sales from a sales territory is $5 million; thus, a company's sales staff can expect to generate $5 million in sales per year that originate from a specific sales territory.
The per annum interest rate charged on a credit card is 36%; this is derived from a 3% monthly rate that is charged on unpaid monthly balances (calculated as 3% x 12 months = 36% on a noncumulative basis).
A monthly magazine charges $5 per issue, so the per annum amount of a subscription is $60.