Address to register as sole trader on a narrowboat

Hi. I live on a narrowboat and travel around the canals with no fixed address, and want to start a small land-based business. To do this, I have tried to register as self-employed- a sole trader- via Government Gateway. I have a fixed business address which is a workshop that I will use, and visit this nearly every day. But the online form also wants a main address, and asks “how long have you lived there?” This means that I can’t use the business address as I was hoping to do, or even a relative’s or friend’s address. It’s a classic “computer says no” situation. There are plenty of continuous cruisers trading from their boats on the canals, so there must be an answer, but what is it?

Hi,
I am sorry for the inconvenience you have experienced in trying to register here.
Please contact us by webchat, phone, or post, via Self Assessment: general enquiries, and we should be able to finalise your registration.
Thank you.