Offshore tax havens is the usual one. Panama papers put only a small dent in that. All sorts of stuff that's been cracked down on in recent years, like "take your salary through a one person company as dividends".

UK had a scheme where people would take out ""loans"" from their employer that would then be "forgiven". I believe this one blew up Rangers football club.

Fun UK example from the 70s: the tax on car parts was much lower than the luxury tax on cars, so people invented the "kit car" which you assembled yourself: the Caterham 7. Still niche popularity today.

Well, for one, people who owned small/medium sized businesses would put effectively their entire family on payroll to cut the businesses’ earnings and lower their tax bill.