Don't make this mistake if you want Trump's capital gains tax break

President-elect Donald Trump
Jabin Botsford | The Washington Post | Getty Images

Many investors are waiting to take any profits on the Donald Trump rally on the notion that if they wait to sell until January, they will benefit from a capital gains tax cut by the new president on their 2017 returns.

It's a theory cited by Dan Clifton of Strategas Research Partners in a note to clients Tuesday. Many strategists, including those at Strategas, believe it's the one reason why this rally is showing no signs of slowing down into year end.

Clifton has a great piece of advice for those waiting to sell in 2017:

"In 2003, when Congress cut the capital gains tax, the provision was made retroactive to the first committee hearing in March. So be careful just selling on January 1st, depending on when Congress acts, the provision may not be in effect at the exact start of 2017."

So investors may want to wait for more details on the proposed tax cut.

More In Pro News and Analysis

CNBC ProStrategists reveal how they're trading tech stocks — and the same names keep coming up
CNBC ProGoldman Sachs picks Chinese stocks with the most room to bounce back as Covid eases
CNBC ProAs stocks edge near bear market, it will be the economy that decides where the sell-off ends