How to Use "In Care Of" (c/o) in a USPS Address — Format, Examples, Rules

In Care Of (c/o) addressing lets you send mail to someone at another person's address or a business location. This is useful when the recipient does not have their own mailing address, is staying temporarily with someone else, or receives mail at a workplace. People often use c/o when mailing to someone staying temporarily at another address or when sending legal or business mail through an intermediary. USPS recognizes c/o as a standard addressing element and will deliver the mail to the address listed.

What Does c/o Mean in an Address?

What does c/o mean on an envelope? "c/o" means "In Care Of." It indicates that the mail should be delivered to a specific address, but the primary recipient is not the usual occupant. The person or business listed after "c/o" is responsible for receiving the mail and passing it to the intended recipient. This keeps the mail from being returned as undeliverable. Is c/o the same as care of? Yes. USPS accepts "c/o," "℅," or the full phrase "Care Of."

Standard c/o Address Format

The correct USPS c/o address format is:

• Line 1: Recipient name (the person the mail is for)
• Line 2: c/o [Name of person or business at the address]
• Line 3: Street address
• Line 4: City, State ZIP Code

Example (personal):

Example (business):

For more details on proper envelope addressing, see our complete addressing guide.

How to Write c/o on an Envelope

How do I write c/o on an envelope correctly? Follow these USPS addressing rules for c/o:

• c/o goes on line 2, directly below the recipient's name and above the street address
• Uppercase is preferred for machine-readability (C/O)
• Do not write "CO" without the slash — always use "c/o" or "C/O"
• Do not replace the street address with the c/o line — both are required
• The c/o name should be the person or business that will physically receive the mail at that address

USPS does not redirect c/o mail to the intended recipient if the c/o party moves. The mail follows the address, not the recipient.

When to Use In Care Of

• Sending mail to someone staying with a friend or relative
• Addressing mail to an employee at their workplace
• Reaching someone at a hotel, hospital, or care facility
• Sending mail to someone who recently moved and lacks a permanent address
• Contacting a person through their attorney, accountant, or other representative
• Mailing certified mail to someone without a known permanent address

c/o vs. ATTN (Attention)

These terms serve different purposes and are not interchangeable:

• c/o (In Care Of): The recipient does not live or work at the address. Someone else will receive the mail on their behalf.
• ATTN (Attention): Used for business mail when you want a specific person or department to handle it. The business is the actual recipient.

ATTN Example:

Using c/o for Legal and Official Mail

Courts, government agencies, and businesses accept c/o addresses for official correspondence. If you need to serve legal documents or send certified mail online to someone without a known address, c/o through their attorney or employer is a recognized method. The certified mail receipt will show delivery to the c/o address.

Will USPS Deliver c/o Mail?

Does USPS deliver c/o mail? Yes. USPS treats c/o as a delivery instruction. The mail goes to the street address listed, regardless of whose name appears on line one. However, the person or business listed after c/o must be willing to accept mail for the intended recipient. If they refuse or if the name is not recognized at that address, the mail may be returned.

Common Mistakes

• Putting c/o on the wrong line (it should be line 2, directly under the recipient name)
• Using c/o when ATTN is more appropriate for business mail
• Not confirming the c/o party will accept mail for the recipient
• Forgetting to include the full street address below the c/o line
• Writing "CO" instead of "c/o" or "C/O"
• Using c/o for PO Box addresses without including the box holder's name

FAQs

Related Guides

• How to Address an Envelope
• How to Avoid Mail Being Returned to Sender
• What is Certified Mail?
• How to Send Certified Mail Online
• USPS Change of Address Guide
• USPS General Delivery Guide
• How to Address a PO Box
• How to Address a Letter to an Inmate
• Return to Sender Guide