I run a group in the UK on meetup.com which offers free walks/hikes in my local area. There are over 200 "members" but I am the only organiser of walks. I don't charge my members and expenses ($15 US = £10 UK per month for meetup.com subscription) are paid out of my own pocket.
I am thinking of starting to charge for the walks - I will give people the option of paying per walk or a yearly subscription. This will cover my subscription and allow me to buy public liability insurance. It would not be run for profit - if there is a surplus, I will simply reduce the subscription/charge in the next year, or put it towards a Christmas meal for the members, or donate it to charity. The annual turnover would be small - less than £400 a year.
My question is this: would I have to register this as a business with HMRC, and would I be required to fill out tax returns each year, or keep accounts?