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Send 8283 separately by mail
Yes, Form 8283 can be mailed attached to Form 8453. One of the checkboxes on Form 8453 is for "Form 8283, Noncash Charitable Contributions, Section A (if any statement or qualified appraisal is required), or Section B, Donated Property, and any related attachments (including any qualified appraisal or partnership Form 8283)."
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