You should not sacrifice your 401(k) nest egg to pay off your mortgage as soon as possible. On balance, that would be a loser, for multiple reasons.

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A reader asks: “My current 401(k) balance is about the same as my mortgage balance. I am 45. Would it make sense to pay off the mortgage with the 401(k)?”

Bad idea!

Looking ahead to retirement, your objective should be to accumulate a 401(k) nest egg of financial assets as large as possible and pay off your mortgage as soon as possible. You should pursue these objectives independently, not sacrifice one to obtain the other. On balance, that would be a loser, for multiple reasons.

Early withdrawal costs

Funds withdrawn from a 401(k) before age 59½ trigger tax payments on the amount withdrawn plus a 10 percent early withdrawal penalty. While there are exceptions to the withdrawal penalty, paying off a mortgage balance is not one of them. That means that paying off a mortgage balance with a 401(k) balance of the same amount would not be a break-even but would generate a sizable cash outflow.

Earnings opportunity loss on the existing 401(k) balance

An even larger loss from liquidating your 401(k) is the future earnings on the funds withdrawn. These earnings accumulate tax free until you are 70½, and at that point you pay taxes only on the amounts withdrawn at your tax bracket at that time, which could be a lot lower than it is now.

Possible earnings opportunity loss on new contributions

If your intention is to abandon your 401(k) after it has been depleted, given that you are still many years from retirement, the largest loss would be the tax-deferred income you could contribute plus the tax-deferred earnings on those contributions that you would be making in future years.

Your major objective should be to contribute as much as possible — I have no advice on that — and obtain as high an earnings rate as possible. I do have some thoughts about that.

Over a period of years, the rate of return on your 401(k) should be well above your mortgage rate. At 45, you should be invested largely if not entirely in common stock.

A diversified portfolio of common stock will generate high rates of return over long periods along with high short-term variability.

For example, during the period 1926-2012, the median return on the common stock of large companies over 25-year periods was 11.34 percent. The highest 25-year return was 17.26 percent while the lowest was 5.62 percent. Over 10-year periods within the same time span, the median return was 10.52 percent, with a high of 21.43 percent and a low of minus 4.95 percent.

As you get closer to the day when you begin drawing funds out of your 401(k) — say, about 10 years before — you should consider shifting as much as half of your 401(k) assets into interest-bearing securities. The reason is that the short-term variability in stock returns can be very costly once you enter the drawdown period.

Your mortgage balance should be paid off by the time you begin drawing funds from your 401(k). If scheduled amortization will not do the job, you should develop an extra payment program that will.

To maintain the discipline needed for a successful extra payment program, make the payments immediately after being paid. Waiting until the end of the pay period is a recipe for failure.