What Does C/O Mean in an Address? Examples and How to Use It

Where does the c/o line go?

The c/o line goes directly under the recipient’s name and above the street address. The street address on the envelope is the address of the c/o person or business.

USPS Publication 28, its addressing standards, says to “Format all lines of the address with a uniform left margin.” The same section says “Uppercase letters are preferred on all lines of the address block,” and it accepts lowercase letters that meet USPS readability guidelines. So “c/o” and “C/O” mean the same thing.

An online form may not have a line for c/o. Look first for a field labeled “care of” or “c/o.” If there is no such field, read the form’s instructions first, because some form lines rule out c/o. If the form allows c/o, the layout depends on the lines it has. With two address lines, the USPS order puts the C/O line first and the street address second. With one street line, the Internal Revenue Service (IRS) instructions for Form 1065 and Form 1120-S show how those two forms handle it. They say to “enter “C/O” on the street address line, followed by the third party’s name and street address or P.O. box.” Read the address back on the confirmation page before you finish.

The table below uses the four-line example from the USPS FAQ.

How to write a c/o address: examples for a person and a business

A business can be on either line. The USPS FAQ refers to “the c/o person or entity,” and IRS instructions describe a partnership or corporation that “receives its mail in care of a third party.” In each row of the table below, the street address belongs to whoever is on the C/O line.

The names and addresses are examples. Add the city, state, and ZIP Code on the last line.

When should you use c/o?

Use c/o when two things are true. First, the person or business on the first line does not normally get mail at that address. Second, someone at that address has agreed to take the mail.

• A guest or relative is staying with you for a while and needs mail at your address.
• You are between homes, and a friend or relative agrees to take your mail.
• Your company gets mail at its accountant’s or attorney’s office.
• Your company gets mail at another company’s address.
• Your company gets mail at a friend’s or relative’s home.

A company that uses c/o relies on the other person or business to hand over its mail. A business can also use an address from a mail service to receive general mail. Our Silicon Valley and Los Angeles pages describe the business addresses save office offers.

When should you not use c/o?

You do not need c/o when the person or business on the first line normally gets mail at the address. A name and a street address are enough.

For an employee at the company that has the address, use an Attn line, which the next section explains.

Do not use c/o in place of a private mailbox number. Publication 28 says “Private companies offering mailbox rental services to individuals and businesses are considered commercial mail receiving agencies (CMRA).” It then says “Mail sent to an addressee at a CMRA must include either the PMB identifier or the #, followed by the appropriate private mailbox number. Use of any other identifier is prohibited.” PMB stands for private mailbox. Our guide to CMRA addresses explains how to check an address.

Do not use c/o across countries on international mail. The USPS International Mail Manual, in its standards for international destination addresses, says “Mail may not be addressed to a person in one country “in care of” a person in another country.”

Do not use c/o on a form line that rules it out. The last section of this guide shows how the wording changes from form to form.

C/O vs Attn: what is the difference?

Attn is short for “attention.” Use Attn when the mail is for a company at that address and you want a certain person there to get it. Use c/o when the mail is for someone who does not normally get mail at that address and a person or business there has agreed to take it.

The two lines sit in different places. Publication 28 says “The Attention Line is placed above the Recipient Line, that is, above the name of the firm to which the mailpiece is directed.” So the Attn line comes first, and the C/O line comes second.

Mail sent to a person at a company’s address still goes to the company. The Domestic Mail Manual says “All mail addressed to a governmental or nongovernmental organization or to an individual by name or title at the address of the organization is delivered to the organization.” Our guide to the “Delivered, Front Desk/Reception/Mail Room” status covers mail handed to a front desk.

Can you use c/o on a business form?

It depends on the form and the line. The USPS format tells you how to write an address. The format does not tell you what an agency accepts on a filing. The table below has five rows quoted from IRS and California forms, and each row applies only to that form and line.

IRS Form SS-4, the application for an Employer Identification Number (EIN), has a line for the name of a “care of” person. The instructions for the mailing address lines add “Generally, this address will be used on all tax returns.” Our guide to addresses on Form SS-4 covers the other lines.

California Form LLC-12, the Statement of Information for limited liability companies (LLCs), shows how one form can treat two lines differently. Its instructions give one rule for the principal office and another rule for the mailing address. Our guide to mailing and physical addresses explains what each kind of address means.

If a form does not mention c/o, read its instructions and ask the agency or a professional before you file. Do not assume that a rule from one form carries over to another form.