Basically if you have written off the loss, then you have a $0 cost based on what you receive so capital gain on whole amount received less 50% discount. If you ended up with a carried forward loss from writing them off then obviously you could use it. If you used the loss against other gains in the year you wrote it off (or subsequent years) your accountant may do variations to prior tax returns reversing out the impact of that loss and then use your cost base in current year. Would wait until you know what you are dealing with before stressing too much about it.
A40 Price at posting:
8.2¢ Sentiment: Hold Disclosure: Held