In-depth analysis of the "hidden killer" in CFD trading - overnight interest (Swap): detailed explanation of interest rate parity theory, rollover mechanism (Rollover) and the fatal "Wednesday triple interest" effect. This article teaches you to use the WMAX trading calculator to estimate the cost of holding positions, provides practical strategies to avoid high interest rates, and helps you achieve a professional leap from "blind holdings" to "actuarial holdings" in the complex interest rate environment of 2026.