Should I sell a winning stock now or hold it to defer the capital gains tax?

Holding has a real, quantifiable benefit: deferring the tax lets the money you'd have paid the IRS keep compounding for you, which is like an interest-free loan. That's the case for letting winners run – tax deferral plus the possibility of a future step-up in basis at death or selling in a lower-income year. But never let the tax tail wag the investment dog. If a position has become an oversized, risky concentration in your portfolio, the danger of holding can outweigh the tax savings; trimming and paying 15–20% is often the prudent move. A middle path: harvest losses elsewhere to offset the gain, donate appreciated shares, or spread sales across tax years. Decide based on diversification needs first, taxes second. Compare scenarios at wealthserene.com/tools/capital-gains.