The maximum amount that your son can transfer from his tuition is based on the amount left over after your child has claimed the tuition amount for his return. Your child can transfer up to $5,000 of the tax credit, less the amount used to reduce tax owing. So if they reduced their tax owing by $1,000, the most that can be transferred is $4,000. 

For more information please see:

Claiming a Tuition Amount From Your Child’s College

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