Case study
Should you sell mutual funds for ETFs and pay the tax?
You've got an old actively managed mutual fund in a taxable account. It's expensive, it's sitting on a nice gain, and every year you look at the ETF that does basically the same thing for a fraction of the fee. Is it worth paying the tax to switch?
Usually the answer is yes, and sooner than most people think. But not always, and the cases where it's a bad idea are worth knowing.
The setup
- $150,000 in an actively managed mutual fund with a 0.85% expense ratio
- You paid $100,000 for it, so there's a $50,000 long-term gain
- 20% all-in tax on that gain (15% federal plus 5% state)
- The alternative is an index ETF with a 0.05% expense ratio
- Both earn 7% a year before fees, so 6.15% vs 6.95% after fees
Switching costs $10,000 in tax today and leaves $140,000 to invest in the ETF.
The thing most people miss
That $10,000 isn't extra tax. It's early tax.
If you keep the mutual fund, the $50,000 gain doesn't go away. Whenever you eventually sell, it gets taxed, along with everything the fund earns in the meantime. Selling now just moves the bill forward. So the real cost of switching isn't $10,000. It's the growth you give up on that $10,000 by paying it sooner.
At 6.15% a year, that lost growth is roughly $600 in the first year. Meanwhile, the lower fee saves you about 0.80% on $140,000, or roughly $1,100 a year. The fee savings win almost immediately.
Comparing spendable money after both paths are sold and taxed, switching pulls ahead within the first year. The hurdle over 20 years is 6.41%: the ETF only has to earn that much to break even, and at 6.95% it clears it by more than half a point a year.
| Years held | Switching leaves you ahead by |
|---|---|
| 3 | +$1,483 |
| 5 | +$2,993 |
| 10 | +$9,331 |
| 20 | +$41,476 |
| 30 | +$129,615 |
After 20 years and all taxes, that's $457,372 if you switch versus $415,896 if you stay. An 0.80% fee gap compounds into real money.
When switching doesn't pay
The math flips when the fee difference is tiny. Say you own a low-cost index mutual fund at 0.04% and you're tempted by the ETF version at 0.03% because ETFs feel more modern. Same $150,000, same $50,000 gain, same 20% tax:
| Years held | Switching leaves you |
|---|---|
| 10 | −$7,473 |
| 20 | −$21,922 |
| 30 | −$49,851 |
A 0.01% savings never earns back the growth lost on $10,000 of early tax. Under these assumptions it doesn't break even within 60 years. If you already own a cheap index fund, the wrapper isn't worth a tax bill.
What else moves the answer
- A bigger gain. With a $50,000 basis instead of $100,000, the tax doubles to $20,000. Switching still wins, but it now takes about 7 years to pull ahead, and the 20-year advantage shrinks to about $18,800.
- Holding for heirs. If you'd never sell and your heirs would get a step-up in basis, the keep path's gain is never taxed. In this example, break-even stretches to about 10 years. Still worth it over a long horizon, but much less obvious.
- Capital gains distributions. Actively managed mutual funds often pay out capital gains every year, taxable even if you never sell. ETFs typically pay out far fewer. The numbers above don't include this, so for most active funds they understate the case for switching.
Check this before you sell
Some fund companies let you exchange certain index mutual fund shares for the ETF share class of the same fund without a taxable sale. If that's your situation, the tax cost may be zero. Ask your fund company first. And if you have multiple purchase lots, the ones you bought most recently may carry little or no gain, so moving those first can get you part of the way for very little tax.
Try it with your numbers
Enter your fund's value and basis, and use returns after fees: subtract each fund's expense ratio from the same expected return.
Run this example in the calculator
Figures assume a single lot, flat tax rates, returns net of fees, the same gross return for both funds, and both paths fully sold at the end of the period except in the step-up case. Capital gains distributions are not modeled. These are illustrations of the arithmetic, not predictions or recommendations. Check your own situation with a tax professional.