if you go into the HM website, go to VAT, go to ready reckoner and in there there is a list of trade sectors. I believe it is any business not listed elsewhere, go into this. (there are 2 linegaes that are similar, but you should find window cleaning in one of them) Keep delving you will find it. A word of caution. depends on what you call your service, we are a cleaning service as we don't just clean windows and the flat rate is 11%. A while ago window cleaning only was different at 10%.