I do work in the legal field, and @ DebbieA, we do not write "percent" when writing out a percentage. We write it as "per cent". Also, I realize this conversation originated quite some time ago, but - speaking from experience - you MUST write out percentages in legal documents. For instance, in a promissory note, you would say that there was a principal sum with interest "at the rate of three and nine-tenths per cent (3.9%) per annum..." Percentages written out can be very tricky though. I still catch myself having to count exactly how many digits over from the decimal point the percentage goes, so that I will accurately reflect that amount when putting it into words.