His method -- buy VISA giftcards at a grocery with his AMEX 5% cash back, then use those giftcards to purchase $$ transfers into his bank account (which would then be used to pay his AMEX bill).
Thanks! Your comment + the headline + basic understanding of tax law supplies the whole story, without needing to engage with their formulaic clickbait.
The other trick I heard is betting on two opposing teams in two betting sites. AFAIK got my mate banned after collecting $70k.