These example sentences are representative of the most common uses of these two phrases and, as one can see, there is no real difference between per annum and per year in usage. As kiamlaluno says, per annum is traditionally used more in financial contexts than per year, but these sentences show that per year is also perfectly acceptable.
What does per annum compounded monthly mean? It means that the rate you are given is an annual rate, but interest is charged each month rather than once a year. Then, if you don't pay there will be interest on the interest the following month. This results in a slightly higher amount of interest than with simple interest.
What does per annum compounded monthly mean? - Legal Answers - Avvo.com
Personally I think "a year" is most likely to be understood as meaning any 12-month period, whereas the 'more formal' "per year" and "out of a year" are more likely to imply a calendar year. Of course, as Phil suggested, you could just say "7 months out of 12".
Does per annum mean compound interest Generally speaking, if interest is stated to be at 8% per annum (and that is all that it says), then this means that there is no compounding going on during the course of the year. So for example if a loan was for $1,000 and bore interest at 8% per annum, this would mean that at the end of a year it would have intererst of $80 (assuming no payments during ...
What does 12 % annum mean on a child support judgment? Is it 12 % interest per year until paid in full or on balance due year? I was awarded a judgment on child support arrears, I needed to know how the interest applies to it. Is it 12 % per year on judgment amount until balance is paid or 12% interest on the balance due each year until paid off.