Tax optimization: fewer moves, but some are required
Sell only when the reason to sell is stronger than the cost of the tax. The goal isn't to never sell — it's to never sell unnecessarily.
TL;DR — Every time you sell a winning position, you pay tax on the gain. Over years, that friction destroys a significant portion of your returns. The goal is to minimize unnecessary taxable events. But some moves are required, and knowing which ones can actually save you money.
Every time you sell a position at a profit, a portion of that gain goes to your tax authority. In most European countries, this ranges from 15 to 30 percent. That sounds manageable for a single transaction. Across 20 years of active rebalancing, it compounds into a serious drag.
The goal is not to never sell. The goal is to sell only when the reason to sell is stronger than the cost of the tax.
When selling is worth the tax hit:
The thesis is broken. If the macro regime underlying a position has changed, you exit regardless of the tax cost. Staying in a dead thesis to avoid taxes is irrational. The position will likely fall further, and you will end up paying taxes on a smaller gain or writing off a loss.
The position has grown so large it creates real risk. If a single position is now 25 or 30 percent of your portfolio because it ran very hard, the concentration risk justifies trimming even if it triggers a taxable event. The risk of that position reversing sharply outweighs the tax friction.
When selling is not worth it:
Rebalancing from a winner to fill a laggard position, when you have fresh capital coming in. If your monthly salary or a bonus is arriving, use that new money to fill the underweight position instead. Same rebalancing outcome, no taxable event.
Reacting to short-term price moves. If a position is down 10 percent in a month but the thesis is intact, do not sell at a loss to "clean up the portfolio." You crystallize the loss and miss the recovery.
The simple rule: Before selling any position, ask: is there a way to achieve the same portfolio outcome using fresh incoming capital instead of a sale? If yes, use the fresh capital. If no, sell and accept the tax.
One practical note: in many countries, losses can be offset against gains in the same tax year. If you have a position where the thesis is clearly broken and it is sitting at a loss, and you have other winning positions you need to trim anyway, doing both in the same year can reduce your total tax bill meaningfully. This is worth thinking about, especially in the final quarter.
Example — An investor needs to rebalance gold from 12 percent back up to 20 percent of the portfolio. Option A: sell part of their equity ETF (a taxable gain) and buy gold. Option B: direct the next four months of savings entirely into gold. Option B achieves the exact same outcome with zero tax. The investor waits. No transaction, same result.