You sometimes hear that you should conduct your portfolio maintenance--checkups, rebalancing, tax-loss harvesting, and so forth--at year-end.

But in reality, waiting until late December is apt to be too late if you're aiming to minimize your tax bill. You may lose your chance to act pre-emptively to avoid capital gains distributions from your mutual funds, for example. And the longer you wait, the more you court the risk that you won't conduct these year-end portfolio maneuvers at all. After all, December is often a busy month, period.