No. Because credit card rewards are considered as Rebates which are not subject to tax.

What you MS, essentially is just to earn rewards on your credit cards. The reward is the SAME for those who never know about MS. It is the benefits for ALL card holders - whether your spend is real spend or manufactured spend, makes no difference.

OTOH, bonuses earned from BANKING PRODUCTS, i.e. checking / saving accounts, are considered as pseudo Interests, hence subject to tax.