Play your credit cards right for extra cash back

New York

FOR years, the holy grail for many seekers of credit card rewards has been a guaranteed 2 per cent back on every dollar they spend.

The problem for startups and for financial services companies both large and small is that it's difficult to make the product profitable. The fees that merchants pay to accept cards won't cover all of those rewards. And it's intensely annoying for consumers who have moved all their spending to find out a year later that their issuer is cutting the reward because it couldn't make the numbers work.

Still, a handful of grown-up operators like American Express (and its partner, Fidelity), Barclays, Capital One and Ci…