Can changing the year of my birth which I made a mistake on, change the amount of my refund?

[Vanessa]

Possibly.  If you are under 24, there are refundable education credits you would not be eligible for.  If you are under 25 and do not have a dependent, you would not be eligible for the Earned Income Credit.  So, if you had a birth year incorrectly listed making you 26 but you are actually 21, you may have lost some refundable credits. 

On the other end of the spectrum, if you are over 65, you get an extra $1,600 added to your standard deduction if you are single or $1,300 if you are married.  You also would not qualify for the Earned Income Credit if you are over 65.