Please explain the meaning of "otherwise than" in this sentence

Please explain the meaning of the second part and explain "otherwise than" in part b

a person’s UK property business consists of:

(a) every business which the person carries on for generating income from land in the United Kingdom; and

(b) every transaction which the person enters into for that purpose otherwise than in the course of such a business.

Solution 1:

every transaction which the person enters into for that purpose otherwise than in the course of such a business.

This appears to mean:

"...every transaction which the person enters into for the purpose of generating income from UK land that is not part of their business."

The clause is nonsense when the logic is examined. It means that transactions that are not part of the business are part of the business. Clearly that is a contradiction.

Maybe this makes sense to lawyers.