Tax-Loss Harvesting and Capital Gains Management in a Taxable Account

Lot selection is the foundation and costs nothing. Every purchase creates a tax lot with its own date and cost basis. When you sell part of a position, most custodians default to first-in, first-out, which usually sells the oldest, lowest-basis shares and realizes the largest gain. Choosing specific identification lets you pick the lots, and it must be designated at or before the trade settles, not after the fact. A sensible default order when raising cash is short-term losses first, then long-term losses, then long-term gains from the highest-cost lots, and short-term gains last. Many custodians let you set a standing method such as highest cost or tax-optimized. Mutual funds may also use average cost, which is simpler but removes lot-level control once elected.

Tax-loss harvesting means selling a position below its cost to realize the loss, then immediately buying something similar so your market exposure stays roughly the same. Losses first offset gains of the same type (short-term against short-term, long-term against long-term), then the other type, then up to $3,000 a year of ordinary income. Anything left carries forward indefinitely and keeps its character. The wash sale rule disallows the loss if you buy a substantially identical security within 30 days before or after the sale. Swapping an S&P 500 fund for a total market fund, or one sector fund for another built on a different index, is a common way to stay invested. The rule reaches further than people expect: a purchase in your IRA, a purchase by your spouse, or an automatic dividend reinvestment within the window can all trigger it. A wash sale caused by an IRA purchase permanently disallows the loss.

Tax-gain harvesting is the less known mirror image. The 0% long-term capital gains rate applies to taxable income up to about $98,900 for married couples filing jointly in 2026 ($49,450 single). In the early retirement years before Social Security and RMDs, many couples have very little taxable income. A couple with $60,000 of other taxable income after the standard deduction has about $38,900 of room to realize long-term gains at 0% federal tax. They can sell appreciated shares and buy them right back, since the wash sale rule does not apply to gains, and reset the basis higher at no federal cost. Arizona taxes capital gains as ordinary income at its 2.5% flat rate, so the state cost is small but not zero. The extra income also raises MAGI, which can affect ACA subsidies, the taxation of Social Security, and IRMAA two years later.

The annual gain budget ties it together. Each January, estimate your ordinary income for the year and decide how much realized gain you can accept before crossing a threshold that matters: the top of the 0% or 15% capital gains bracket, the 3.8% net investment income tax, which applies above $250,000 of MAGI for joint filers ($200,000 single) and is not indexed for inflation, the ACA 400% of FPL cliff, or an IRMAA tier. That budget then governs rebalancing trades, withdrawals from the taxable account, and any gain harvesting. Harvested losses expand the budget. A large unplanned gain, such as a fund distribution or a forced sale, consumes it.

Mutual fund distributions are the part of the budget you do not control. Actively managed funds, and some index mutual funds, distribute realized capital gains to shareholders each year, usually in November or December, and you owe tax on them even if you reinvest. Fund companies publish estimates in October. If a fund you own in a taxable account is expected to make a large distribution and you have a loss or a small gain in it, selling before the record date can avoid the distribution. Avoid buying a fund in a taxable account just before its distribution date. Over time, moving from high-distribution mutual funds to tax-efficient ETFs, done within the gain budget, reduces this problem at the source.

Direct indexing scales loss harvesting by holding the individual stocks of an index rather than one fund, so losses can be harvested on individual names even when the index is up. It is most useful for larger accounts with ongoing gains to offset, such as a concentrated stock unwind or a business sale, and its benefit fades as the easy losses are used up. The mechanics and trade-offs are covered in a separate article on direct indexing versus index funds. The lot-selection, wash sale, and gain-budget rules above apply either way.

The endgame of capital gains management is often not selling at all. Assets held until death generally receive a step-up in basis, and in Arizona, community property can receive a full step-up for the surviving spouse at the first death. That makes your lowest-basis lots the ones to hold longest. For charitable giving, donating long-term appreciated shares to a charity or donor-advised fund avoids the gain entirely and generally provides a deduction at fair market value, subject to AGI limits. Give the most appreciated lots, keep the cash you would have donated, and use it to rebuy the position at a higher basis.

Log into your brokerage account and check the default cost basis method. If it says first-in, first-out, change it to specific identification or a tax-optimized method, and confirm how each sale's lots are chosen. This single setting can meaningfully reduce the gains you realize on routine withdrawals.

Turn off automatic dividend reinvestment in taxable accounts where you plan to harvest losses, and direct dividends to cash instead. Reinvest manually as part of rebalancing. Check your IRA and your spouse's accounts before harvesting so a purchase there does not wash out the loss.

If you are in the years between retirement and Social Security or RMDs, look for 0% gain harvesting room every fall. Estimate your taxable income, find the gap below about $98,900 for joint filers, and weigh the benefit against ACA subsidy and IRMAA effects. The same room may be better used for Roth conversions in some years; the two compete for the same low-bracket space.

Keep a running record of loss carryforwards from year to year. A large loss harvested in a down market can offset gains for many years, and it is often the key that makes it affordable to diversify a concentrated position or move out of high-distribution funds.

Coordinate the taxable account with your estate and giving plans. Highly appreciated lots that you may not need are often better held for the step-up or given to charity than sold, and your withdrawal plan should draw from high-basis lots first.

• Leaving the custodian's first-in, first-out default in place and realizing the largest possible gain on every sale.
• Harvesting a loss in a taxable account while the same fund is being bought in an IRA or a spouse's account, triggering a wash sale that can permanently disallow the loss.
• Letting automatic dividend reinvestment buy a few shares within 30 days of a harvest and wash part of the loss.
• Skipping 0% gain harvesting in low-income early retirement years and later selling the same shares at 15% or higher.
• Harvesting gains or doing conversions without checking the effect on ACA subsidies, Social Security taxation, or IRMAA two years later.
• Buying an actively managed mutual fund in a taxable account weeks before its annual capital gains distribution.
• Selling highly appreciated shares to fund charitable gifts instead of donating the shares directly.