Almost every card bonus carries a requirement to spend a certain amount within a set number of months. The structure exists because the bonus is an acquisition cost the issuer must earn back, and spending is the only mechanism that earns it.
Acquiring a cardholder is expensive
Between marketing, underwriting, card production and fraud screening, opening an account costs the issuer a substantial sum before any revenue arrives.
The bonus sits on top of that. It is the largest single item and it is paid out early, which makes the first year of an account structurally loss-making.
Recovering that outlay requires the cardholder to use the card, and use it for long enough that the flow of fees and interest overtakes the upfront cost.
Interchange makes spend the repayment mechanism
Every purchase generates interchange revenue for the issuer, taken as a small share of the transaction and paid by the merchant.
A threshold is simply the volume of spending at which that revenue becomes meaningful relative to the bonus. Setting it higher shifts more of the recovery forward.
This is also why thresholds vary with the size of the bonus. Larger rewards require proportionally larger spending because they must be funded the same way.
The time limit filters for real usage
The window matters as much as the amount. A threshold spread over years could be met by incidental spending on a card that is otherwise dormant.
Compressing it into a few months forces the card into a primary position in the wallet, where habits form. Payment habits are persistent, so a card used heavily in month two tends to still be used in year two.
The requirement is therefore testing for engagement rather than for the money itself.
What counts is narrower than it looks
Qualifying spend usually excludes balance transfers, cash advances, gambling transactions and payments treated as cash equivalents, because none of them generate ordinary interchange.
Fees charged by the issuer, including the annual fee, are generally excluded too. They are revenue rather than spending.
Returns are netted off, so a large purchase later refunded can pull the total back below the line after the bonus has been counted as earned.
Why issuers police repeat applicants
Shoppers who open accounts purely for bonuses never reach the point of repayment, so issuers impose rules limiting how often a bonus can be claimed.
Restrictions based on how recently an account was held, or on how many new accounts have been opened across the market, are aimed at that behaviour.
The rules look arbitrary from outside, but each one is a filter against the case where the bonus is paid and the revenue never follows.