The practical challenge when tax loss harvesting is maintaining a continuous asset class exposure at target levels without time gaps, while avoiding penalties under the IRS Wash Sale Rule (IRC Section 1091).

The problem with time gaps is that significant market moves can occur in the 30-day waiting period of the Wash Sale rule, which would prevent the portfolio from achieving the risk and return expectations on which the portfolio asset allocation was designed.

The solution to the problem is substitution. Immediately upon realizing a loss in one fund, open a position in an alternate fund that is similar to, but not “substantially identical” to, the fund on which the loss was realized.

After the waiting period of 30 days, close the substitute fund position and reopen the original position (assuming …