I believe that the money exchange must occur during the year for the claim of a capital loss. Usually, tax-loss selling for those wanting back in to a stock would be early in the month of December, so they can re-establish a position 30 days later in January.

Anyway, found a couple of articles on Tax Loss Selling...

First this:

http://www.theglobeandmail.com/globe-investor/investment-ideas/features/investor-clinic/selling-your-dogs-can-help-to-curb-your-tax-bill/article1393459/

Excerpt:

"In Canada, the last day for tax-loss selling in 2009 is Dec. 24. That's because it takes three full business days for a trade to settle, and Canadian stock markets are closed on Friday, Dec. 25 and Monday, Dec. 28 (in lieu of Boxing Day). Remember that markets close at 1 p.m. on Dec. 24. In the United States, the last trading day for settlement in 2009 is Dec. 28.

If you miss the deadline, your capital loss will be recorded in 2010. Therefore, you won't be able to use it to offset capital gains in 2009, unless you wait a year and carry the loss back, in accordance with the conditions stated above."

And then this:

http://howtoinvestonline.blogspot.com/2009/12/tax-loss-selling-explained-what-why-and.html

Excerpt:

"The December 31st deadline for transactions (trades of stocks and mutual funds at latest Dec.24th) to count in the 2009 tax year is fast approaching. Take a look at your taxes for past capital gains and your portfolio for paper losses to see if there is an opportunity to gain from tax loss selling."