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where does the adress go on a letter
The return address should be written in the top right-hand corner of the letter. The inside address should be written on the left, starting below your address.
where does the adress go on an envelope
Write the return address in the top left corner. Then, write the recipient's address slightly centered on the bottom half of the envelope.

Question: how about for a business
Self-contained rewrite: where does the business name go on the envelope when sending mail