It depends on why you are asking the question.
To claim educational benefits, the 5 month rule does not apply. Any amount of time as a full time student counts. As others have indicated, you only need to be half time or more to claim educational tax benefits.
The 5 month-full time rule applies to the ability of your parents (or any other relative) to claim you as a "Qualifying Child" dependent. If you were only in school Jan.- April, you do not qualify. If the semester ended May 1, or later, you do qualify.
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There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. They are interrelated but the rules are different for each.
A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
- He is under age 19, or under 24 if a full time student for at least 5 months of the year, or is totally & permanently disabled
- He did not provide more than 1/2 his own support.
- He lived with the parent (including temporary absences such as away at school) for more than half the year
