Make sure you know how to use per cent and percentage. per cent comes after a number. percentage comes after words like the, a, this, that, etc. and is often preceded by an adjective, e.g. A high percentage of customers... Both go with the preposition of. When writing numbers or percentages, use words up to the number ten, e.g. eight per cent, and then figures, e.g. 12 percent. However, always write a number at the beginning of a sentence in words, e.g. Twelve per cent...