CAT bundles the interest rate, fees, mandatory insurance and, where it applies, VAT into a single annual percentage. Banxico (Mexico's central bank) built it so two loans of the same type can be compared head to head. When you see "from 38% CAT", that "from" is calculated on the best-profile customer — yours may differ. If a credit card and a personal loan show the same CAT, the actual total cost works out the same.
An example that settles it: a personal loan at a 32% rate «with no fees» can carry a 38% CAT, while one at 36% with a financed opening fee lands at 41%. The loose rate misleads; the CAT bundles everything. That's why Banxico requires it on any formal offer.
Where you see it in your contract: on the cover page, top, in bold. On fast-loan SOFOMs the real CAT runs from 150% to over 300% — that's not fine print, it's the cost of getting money in minutes with little checking. Always compare two CATs of the same product type; comparing a card's CAT against a mortgage's tells you nothing.