C/O (In Care Of) vs ATTN on Mail

What C/O Means

C/O means “care of.” Use it when you are sending mail to someone through another person or business. The name on the C/O line is the person or organization receiving the mail at that address and making sure it reaches the intended recipient.

Here is a hypothetical example using The Letter Pilot. Say someone wants to send mail to John Doe through our company. They would write John's name on the first line, followed by C/O The Letter Pilot on the second line, and then The Letter Pilot's complete mailing address. The C/O line shows that John Doe is the intended recipient and that The Letter Pilot is the organization receiving the envelope on his behalf.

Standard C/O Address Format

Write the address in this order:

1. The person the mail is for
2. C/O followed by the receiving person or organization
3. The delivery address
4. City, state, and ZIP Code

Keep the recipient block centered on the envelope, and place the return address in the upper-left corner.

When to Use In Care Of

• Sending mail to someone staying with a friend or relative
• Reaching someone through an attorney, accountant, or representative
• Mailing to a guest at a hotel or a patient at a care facility
• Sending mail to someone who temporarily receives mail through a business
• Addressing mail to someone through the holder of a PO Box

Confirm that the person or organization named after C/O is willing to receive the mail before sending anything important.

Using C/O for Legal and Official Mail

A c/o address tells USPS where to deliver an envelope. By itself, it does not prove that a summons, notice, or other legal document was served correctly. Simply writing C/O before someone's name does not establish that the person is legally authorized to accept service.

Certified Mail can provide a mailing receipt and electronic verification of delivery or an attempted delivery. A Return Receipt can provide a delivery record that includes a signature. Those USPS records may be useful, but whether they satisfy a legal requirement depends on the court, agency, contract, and applicable law.

If a deadline or formal notice is involved, check the governing rule or get legal advice before relying on a c/o address.

How C/O Delivery Works

USPS attempts delivery at the address written on the envelope. The C/O line tells the person or organization receiving mail there who the envelope is meant for. Once USPS delivers it to that address, the person or business named after C/O normally passes it to the intended recipient.

USPS says mail is delivered as addressed and that either person may sign for mail addressed to one person in care of another. The receiving party may refuse a mailpiece. Mail that cannot be delivered as addressed or is refused may be returned to the sender, depending on the mail class and circumstances.

So What About ATTN?

ATTN is used when someone is sending mail to a company but wants a specific person or department to receive it. For example, someone might send a letter to The Letter Pilot but want it brought to my attention. See why they call it ATTN?

In that case, the envelope would name me on the attention line and The Letter Pilot as the company receiving the mail:

Frequently Asked Questions