U.S. stocks have had a great year in 2017. The Standard & Poor’s 500 stock index is ahead 18.66% for 2017 as of the close today, December 22. The NASDAQ Composite, heavy on tech stocks and financials, is ahead 28.2%.

But there’s a good likelihood that you’ve got a tax loss or two–not everything you own is up for the year, probably, and not everything you own is up since you bought it way back whenever–and in a year like this tax losses can be especially valuable. Maybe you sold something–at a profit during a brief market hiccup like we had at the beginning of December. Or maybe you decided to take profits in one of your winners ahead of a tuition bill. Or so that you can rebalance a portfolio in 2018.

In any of those cases you’ve got a profit that you’ll have to pay taxes on come April 2018–and it will pay to reduce that profit as much as reasonable by selling a position or two at a loss before 2017 comes to an end.

Notice I wrote “as reasonable” and not “as possible.” You don’t want to sell anything now that you’re likely to want to rebuy within 30 days. The rules say that you have to be out of a position for at least 30 days in order to claim a loss. And you don’t want to sell anything even if it’s a losing proposition now if the recent trend has been upward and the stock looks, finally, to be headed higher.

So in my Jubak Picks Portfolio, for example, I’m going to hold onto my underwater position (down 53.33% as of the close on December 22) in Synaptics (SYNA) because it finally looks like the company has regained its sales traction.

But I’m going to sell what was once a position in OncoGenex Pharmaceuticals because this biotech stock has never recovered from the failure of a drug candidate way back in 2016 and because after a merger I’m not even sure I’d call it a biotech any more. And I’m also going to sell my losing position in Hain Celestial Group (HAIN.)

I bought Hain Celestial Group back on March 26, 2015 because I saw acquisition activity heating up in the natural and organic foods space and I thought Hain’s mix of brands made the company an attractive acquisition candidate. But getting full (or better) value for those assets required a buyer and Hain managed to damp any potential interest there might have been by discovering major accounting problems that took almost a year to fully resolve. No potential acquirer was willing to step in until they knew what they were buying and resolving those accounting issues took long enough so that the bloom is off the natural and organic acquisition rose–especially after Amazon (AMZN) dove into the space through its acquisition of Whole Foods Market this year. The shares are down 34.93% since I added them to this portfolio back on March 26, 2015.

I should have sold OncoGenex last December but I just never got around to writing the post that would have pulled the trigger on that sale. My apologies.

I bought OncoGenex (then trading under the ticker OGXI) for its promising pipeline of cancer drugs. But then the leading candidates in that pipeline failed in clinical trials, first in September 2015 and then even more damagingly in September 16 when the company had to announced bad news on custirsen, a potential drug for prostate cancer. My hope was that the company’s research platform was vigorous enough to allow a recovery from those failures–or at least that some larger drug company would find value in that platform. But that just wasn’t the case. OncoGenex was finally acquired by Achieve Life Sciences, a then private company working on a drug to address nicotine addiction in smokers. The deal was mostly valuable to Achieve because by acquiring a public company it could achieve public company status itself without having to go through the entire expensive IPO process. (The Achieve website notes that the combined company continues work on trials for a cancer drug but it’s clear to me, at least, that the company’s focus is on the smoking market.) I don’t see any reason to hold onto this position. The tax loss is more valuable at this point in a bull market.

These aren’t the only two stocks I’m looking at for end of the year tax selling. I’ve got a candidate or two in my long-term 50 Stocks portfolio. I’ll tell you about them in a post right after Christmas.