Various forms (especially online) ask your marital status. I resent ticking a box that says 'divorced/separated' as I have been divorced some dozen years now and feel truly 'single'. However, could anybody penalise me for saying 'single'? I really don't see what the heck it's got to do with, say, buying a car breakdown service as I was today!
The information is usually used to assess the demographic of the customers using any particular service, so nothing will be lost by advising you are single - it's not legally binding, so don;t worry about it.
I agree. I am a happy "single" and how I got there is no-one's business. However, (joke alert!!) in the case of the car breakdown service it is vitally important as the cost to you of the wife using the car will be astronomical.