My earning music from music days were beyond the 20 year limit.
Which is a shame as now I understand the tax system I would have been able to claim a tax rebate as what I spent on gear, practice venues and recording was more than I ever got back.
These days many people will come under the £1000 turnover de-minimis rule. A three-piece getting paid £250 a gig could do one a month, for example.
And if you do earn more, it's a good reason to make sure you have the finest basses and amps in the land "That 62 Jazz isn't a luxury, think how much tax I've saved!" 🙂