Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
Yes she would as there is a connection between the two businesses, she being a Sole Trader.
Given that the two businesses are distinct in the type of services they offer, then it would be worth incorporating one or both. I would comment that if some customers deal with both businesses, then HMRC may take that as an indication of an artificial separation, and take action accordingly.
I am so sorry to have to rain on your wife's parade.
I am of the opinion that you should declare at 20%.
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