It depends on what you are really asking. You may only claim educational expenses in the year you actually pay them and the education expenses must be for the year you actually took the classes. There is one exception, best explained by example: you may claim on your 2015 tax return expenses you paid in 2015 for classes starting early in 2016.
You may not claim an education credit on your 2016 return for classes in a previous year, regardless of what year you paid those expenses.
However, if you attended class and paid expenses in 2014 (for example), and you (or your parents if your were their dependent) failed to claim a credit on your 2014 return, you may now file an amended 2014 return to claim the credit.
