Mistake #1
You withdraw money from and make a contribution to your TFSA in the same year without regard to your TFSA Limit.
For example, assume that you always contribute the maximum annual amount of $5,500 to your TFSA and you have no contribution room carried-forward from a previous year. If you contribute $5,500 to your TFSA in March 2013 and withdraw $3,000 in June 2013, then you will not be allowed to re-contribute to your TFSA in 2013. You must wait until 2014 to make a contribution to your TFSA again. However, in 2014, your TFSA contribution limit will be $8,500 ($5,500 annual contribution room + $3,000 amount withdrawn from previous year).
Mistake #2
You have more than one TFSA and you don't keep track of your contributions.
In the situation where you have more than one TFSA account (e.g. you have TFSA accounts with different banks), it is your responsibility to keep track of the amount of contributions that you make. Remember that if you over-contribute, you will be charged penalties on the over contribution amount.
