Short answer
No, a P.O. box generally cannot be used as a registered agent address. States require a physical street address in the state where a person can accept legal documents in person during business hours. A P.O. box, a mailbox rental, or a virtual mailbox does not meet that standard because there is no one present to receive service of process. The address on file must be a real, staffed location.
The purpose of the registered agent address is in-person delivery of legal notices, so states insist on a physical street address rather than a mailing address. A P.O. box or private mailbox forwards mail but has no one available to accept a process server handing over Service of process, which is why those addresses are rejected for this role. Some states will note the distinction explicitly on their forms.
If you do not have a suitable street address in a state, or you do not want to publish your home or office address, a Commercial registered agent provides a compliant in-state street address and staff to receive documents. That keeps your filing valid and your personal address off the public record. A P.O. box can still be used for general business mail, just not for the registered agent appointment.
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