Does the school report, sent through the Common App, count as an "official transcript?"

Applying to College Common and Coalition Application
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Or do I need to mail it?

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@Happi-chan - if uploaded by the GC, it will count as official transcript. If college requires something else, they will request it - most likely directly to your GC.

You as an applicant should not be mailing transcripts, unless it is in sealed envelope.