How Tax-Loss Harvesting Works
Tax-loss harvesting is a strategy of intentionally selling positions with unrealized losses to realize those losses, then offsetting them against gains from other investments to reduce your tax burden. For example, if you realized 50 man-yen in gains from Fund A and Fund B has 30 man-yen in unrealized losses, selling Fund B to lock in the loss reduces your taxable amount to 50 - 30 = 20 man-yen. The tax savings amount to 30 man-yen × 20.315% ≒ 6.1 man-yen.
If you immediately repurchase a comparable product to Fund B, your portfolio composition remains virtually unchanged while only your taxes decrease. However, buying back the exact same security immediately after selling may be treated as a wash sale, so switching to a different fund that tracks the same index is the safer approach.
Long-Term Tax Savings Simulation
Let's examine the long-term impact of tax-loss harvesting. If an investor earning 50 man-yen in annual gains harvests 10 man-yen in losses each year, the annual tax savings are approximately 2 man-yen. Reinvesting that 2 man-yen at 5% annual return over 20 years grows to approximately 66 man-yen.
Furthermore, loss carryforward provisions allow you to carry losses forward for up to three years even in years with no gains. For example, if you realize 100 man-yen in losses this year and earn 80 man-yen in gains next year, you can offset the carried-forward loss to bring the taxable amount to zero. The tax savings amount to 80 man-yen × 20.315% ≒ 16.3 man-yen.
Timing and Key Considerations
Tax-loss harvesting is typically performed at year-end (December). You review the year's realized gains and unrealized losses, and execute the strategy when offsetting provides a clear benefit. If your annual gains are zero or negative, you can still realize losses to use as carryforward deductions in subsequent years.
Losses within a NISA account cannot be used for gain-loss offsetting. Even if you sell a losing position in your NISA account, you cannot offset it against gains in a Tokutei account. Tax-loss harvesting is only effective in Tokutei accounts (or Ippan accounts). Practical books on gain-loss offsetting walk you through the specific procedures for reporting offsets on your tax return.
Significance for Long-Term Investors
When you reinvest the tax savings from harvesting, the compound effect generates a significant difference over time. Saving 5 man-yen in taxes annually for 20 years and investing those savings at 5% yields approximately 165 man-yen. The appeal of this strategy is that it transforms the seemingly negative act of realizing losses into a proactive wealth-building tool.
However, if trading commissions or redemption fees apply, verify that the net benefit exceeds these costs. At online brokerages, mutual fund trading is often commission-free, keeping the cost barrier low. Books on taxes and asset management help you organize account strategies for maximizing after-tax returns.
Next Steps - Conduct a Year-End Gain/Loss Review
As year-end approaches, check your Tokutei account's annual trading report (interim) to identify your realized gains and unrealized losses. If you have losing positions that can offset your gains, sell them before year-end to lock in the losses. After selling, switch to a different fund tracking the same index to maintain your portfolio.
Try our simulator to see the long-term impact of reinvesting your tax savings. You will find that small, consistent tax savings compound into a meaningful difference over time.