In Russia, Kazakhstan and Belarus
Russia
Cashback under banks' loyalty programs is, as a rule, not subject to personal income tax (НДФЛ, NDFL), unless it is payment for work or services (clause 68 of Art. 217 of the Tax Code). The terms — categories, monthly limit, crediting periods — change; check them in your card's tariffs.
Kazakhstan
In Kazakhstan, cashback and bonuses on cards are also common; each bank sets its own terms.
Belarus
In Belarus, banks pay cashback on cards on their own terms, usually with a monthly limit.