High Yield, Capped Gains: Mechanics, Trade-Offs, and Practical Diagnostics for Covered-Call ETFs

Covered-call ETFs offer high yield with capped gains: they turn part of expected equity upside into option-premium income. The income is real, but it comes with structural trade-offs: upside is capped above the strike, outcomes are path-dependent, and distributions may include return of capital (ROC) that reduces principal over time. This primer explains the basic mechanics, the main risk characteristics, and the implementation choices that drive results (such as option moneyness and reset frequency). We use simple payoff intuition and stylized NAV sketches, then contrast common U.S. products with UCITS variants to show how design differences matter in practice. The core message is practical: covered-call ETFs can play a role as income complements in diversified portfolios, especially in sideways markets with reasonably firm implied volatility, but they are generally unsuitable as long-term growth anchors. Investors should judge these funds on total return and the sustainability of distributions, not headline yield alone.