What this is
The exchange runs a limited-time promotion. Inside that window, the headline rate is the rate paid; outside it, the product reverts to a baseline that is typically not disclosed on the product page and must be retrieved from the terms and conditions. Third-party rate aggregators capture the current headline value and present it as the product’s standing APR, which compounds the misread.
What it means for you
Annualizing the headline APR almost invariably overstates realized return. Promo windows typically run two to six weeks; for the remaining ten or eleven months the product accrues at its baseline. A 60-70% gap is common, an 8% headline against a 3% baseline. For planning purposes, anchor expectations on the baseline; treat any additional interest from the promo window as a one-off, not a steady yield.
In practice
Consider a CEX USDT promo product: headline APR of 8%, promo window 2026-04-17 to 2026-05-15. Outside the window, the product settles at a baseline of roughly 3%, a figure absent from the product page and recoverable only from the terms and conditions. A 10,000 USDT deposit held for a year accrues at 8% for roughly one month and at 3% for the remaining eleven, producing an effective annual yield of approximately 3.4%, about five percentage points below the headline.