Have you ever seen the abbreviation p.a.?
As in the sentence:
Sales increased by 5 per cent p.a.
The abbreviation p.a. is short for per annum and is a Latin phrase meaning per year.
You might know that I’m not a big lover of abbreviations, as I find they can often confuse people. I’d rather use the full term.
So I suggest writing:
Sales increased by 5 per cent per year.