Tax-loss harvesting is one of the few genuine free lunches in investment management — a technique that can improve after-tax investment returns without requiring any additional risk, any predictive skill, or any assumption about which direction markets will move.
The concept is simple: when an investment has fallen in value, you sell it to crystallise the loss, use that loss to offset taxable capital gains elsewhere in the portfolio, and immediately reinvest the proceeds in a similar asset to maintain your market exposure. The tax saving is real; the portfolio barely changes.
For internationally mobile investors who may have gains in multiple jurisdictions, complex asset mixes, or access to particularly favourable capital gains rules in their country of residence, tax-loss harvesting can be especially valuable. But it requires care — particularly around "wash-sale" rules in the US, the UK's bed-and-breakfast rules, and the practical challenges of maintaining portfolio positioning across cross-border portfolios.
How Tax-Loss Harvesting Works
The basic mechanics:
Suppose you hold two investments:
- Position A: a global equity ETF purchased for £100,000, now worth £130,000 (gain of £30,000)
- Position B: an emerging market ETF purchased for £40,000, now worth £32,000 (loss of £8,000)
If you want to take profits from Position A, you would ordinarily pay CGT on £30,000. But if you sell both Position A and Position B in the same tax year, your net gains are £22,000 (£30,000 gain minus £8,000 loss), reducing your CGT bill accordingly.
Better still — if you immediately reinvest the £32,000 proceeds from Position B into a different but similar emerging market ETF, your portfolio exposure barely changes. You still have emerging market equity exposure. You have simply changed which fund holds it, and in doing so crystallised a useful loss.
The benefit: Reduced current-year CGT. The unrealised gain in the replacement ETF carries forward, but this is a genuine deferral benefit — you have the use of the saved tax money in the interim, and if your circumstances change (lower income year, change of tax residence, transfer of assets), the deferred gain may ultimately be taxed at a lower rate or not at all.
UK Capital Gains Tax: The Framework
For UK resident investors, tax-loss harvesting operates within the UK CGT rules:
Annual exempt amount: The CGT annual exemption is currently £3,000 (2025–26 onwards, following significant reductions from the previous £12,300). Gains below this amount are exempt from CGT, and losses can be carried forward or used against future gains.
Loss rules: Capital losses in a tax year are automatically set against capital gains in the same year. Unused losses can be carried forward indefinitely (but must be reported to HMRC within four years of the tax year in which they arose).
UK rates (as of 2026): 18% for basic rate taxpayers, 24% for higher and additional rate taxpayers (equalised for most assets following the Autumn 2024 Budget changes). The higher rate on residential property gains has been retained at 24%.
Tax year timing: the UK tax year runs 6 April to 5 April. Tax-loss harvesting decisions must be executed on or before 5 April to count in the relevant tax year.
The Bed-and-Breakfast Rule
The main technical complication for UK investors is the bed-and-breakfast rule (Section 106A of the Taxation of Chargeable Gains Act 1992).
If you sell an investment at a loss and repurchase the same investment within 30 days (before or after the sale), HMRC disregards the disposal for CGT purposes. The loss is not crystallised. The repurchased shares are matched with the sold shares under the 30-day rule, and no tax benefit arises.
This prevents investors from "selling and immediately rebuying" to crystallise artificial losses while maintaining the same economic exposure.
The solution: Replace the sold investment with a similar but not identical investment for at least 30 days. For example:
- Sell iShares MSCI World UCITS ETF → reinvest in Vanguard FTSE Developed World UCITS ETF
- These ETFs track different (though closely correlated) indices. They are not the same investment and the 30-day rule does not apply
- Exposure to global developed equity markets is maintained throughout
- After 30 days, you can switch back to the original ETF if preferred (though this generates a new disposal)
The 30-day window introduces slight portfolio tracking error relative to the original position. In practice, for investors using broad market ETFs tracking similar indices, the deviation is minimal.
The US Wash-Sale Rule
For US citizens and Green Card holders living abroad, tax-loss harvesting is complicated by the wash-sale rule (Internal Revenue Code Section 1091).
Under the wash-sale rule, if you sell an investment at a loss and purchase a "substantially identical" security within 30 days before or after the sale, the loss is disallowed. It is instead added to the cost basis of the replacement security (deferred rather than permanently lost).
Definition of "substantially identical": The IRS has never fully defined this, creating uncertainty. Selling Vanguard's S&P 500 ETF and buying iShares' S&P 500 ETF within 30 days is likely a wash sale because both track the same index. Selling a US equity ETF and buying an international equity ETF is not. Selling a US large-cap ETF and buying a US small-cap ETF is unclear.
The safe approach for US persons is to replace the sold ETF with one tracking a materially different index — for example, switching from S&P 500 to Russell 2000, or from US total market to MSCI ACWI ex-US.
Note that UCITS ETFs and US-listed ETFs tracking the same index may also be treated as substantially identical by the IRS — the analysis is based on the underlying economic exposure, not the fund's legal form.
Cross-Border Complications
International investors may face additional layers of complexity:
Different tax years: The UK tax year ends 5 April; the Australian tax year ends 30 June; the US tax year ends 31 December. An investor who is UK resident for part of the year and Australian resident for part may have gains and losses that fall in different tax years depending on when disposals occur.
Foreign tax credits: If tax has been paid in one jurisdiction on a gain, the investor may be entitled to a foreign tax credit in another jurisdiction to avoid double taxation. This affects the net benefit of tax-loss harvesting.
Offshore income gains: For UK resident investors, as discussed in our article on offshore fund reporting status, gains on non-reporting offshore funds are taxed as income, not capital gains. Losses on non-reporting funds are "offshore income losses" and can only be set against other offshore income gains, not against regular CGT gains.
Change of tax residence: Moving between countries mid-year can create dual-year allocations for gains and losses. In some jurisdictions, departure triggers a deemed disposal that creates gains or losses without a corresponding sale.
When Tax-Loss Harvesting Adds the Most Value
Tax-loss harvesting is most valuable when:
Capital gains tax rates are high: In the UK at 24%, the tax saving from a crystallised loss is significant. In jurisdictions with zero capital gains tax (UAE, Cayman Islands), there is no tax saving to achieve.
You have significant realised gains in the same tax year: If you have sold a business, property, or other investment with a large gain, offsetting it with harvested losses is very valuable.
You have positions with embedded losses: Harvesting only adds value if you actually have positions trading below your cost base. After sustained bull markets, portfolios may have few or no loss positions available.
You are a higher or additional rate taxpayer: The saving from a crystallised loss equals the loss amount times the applicable CGT rate. At 24%, a £10,000 harvested loss saves £2,400.
You can replace the sold investment with something similar: If no suitable replacement exists, you risk being out of the market during the recovery period.
Practical Implementation for International Investors
Step 1: Review portfolio annually for loss positions
Before the end of the tax year, calculate the embedded gain or loss on each position. Flag positions with losses exceeding a threshold (£5,000 or more, for example).
Step 2: Identify offsetting opportunities
Do you have gains to offset? Check realised gains already taken in the year, planned disposals before year-end, and carry-forward gains from prior years.
Step 3: Select replacement investments
Identify suitable replacement ETFs or funds that provide similar but not identical exposure. Document the basis for the replacement selection.
Step 4: Execute the trades
Sell the loss position and buy the replacement. Time the trades to minimise market exposure gap — ideally sell and buy on the same day.
Step 5: Wait 30+ days before repurchasing original
Maintain the replacement for at least 30 days if you wish to switch back. Or hold the replacement permanently if it is equally suitable.
Step 6: Record and report
Maintain records of original cost bases, sale proceeds, replacement purchases, and the tax calculation. Report losses on your self-assessment return (for UK residents) to crystallise them officially.
Automated Tax-Loss Harvesting: Direct Indexing
In the United States, a category of investment management called "direct indexing" has emerged that automates tax-loss harvesting at the individual security level. Rather than holding a single S&P 500 ETF, the investor holds the 500 underlying stocks directly. The manager automatically harvests losses on individual stocks whenever they fall, while maintaining index-like exposure.
Direct indexing services are available in the US for portfolios of typically $250,000 or more. UCITS-equivalent products are beginning to emerge in Europe and internationally, though the market is less developed.
For investors with large taxable portfolios and significant CGT exposure, direct indexing can generate tax alpha (additional after-tax return from systematic harvesting) of 0.50–1.50% annually in well-managed portfolios.
Compliance Caveats
Tax law is complex and varies by jurisdiction. The information in this article is general in nature and does not constitute personal tax advice. UK CGT rules, US wash-sale rules, and the tax treatment of investment losses in other jurisdictions change over time. The interaction of cross-border rules on internationally mobile investors requires specialist advice. Losses cannot be guaranteed and all investments can fall in value as well as rise. Always seek professional tax advice before implementing a tax-loss harvesting strategy, particularly if you have multi-jurisdictional tax obligations.
How Global Investments Can Help
At Global Investments, we incorporate systematic tax-loss harvesting reviews into the annual portfolio management process for clients with taxable investment accounts. We work with tax specialists in each relevant jurisdiction to ensure that the strategy is implemented correctly and that cross-border interactions are managed appropriately. Contact us to discuss whether tax-loss harvesting can improve the after-tax performance of your portfolio.
This article is for general information only and does not constitute financial, legal or tax advice. Rules, prices and regulations change; verify current requirements with a qualified adviser before acting.