Glossary Phone numbers
What is LOA?
Also called letter of authorization, letter of agency
A Letter of Authorization is the document you sign to confirm that you are entitled to move a phone number, and that you authorise the new carrier to request it on your behalf. It is the piece of paper that makes a port request legitimate, and no carrier will process a port without one.
Why the details have to match exactly
The LOA is checked against the losing carrier's billing record, character by character in places. The most common cause of a rejected port is an address that is right in substance but not in form, "Suite 7460" against "STE 7460", or a business name that has changed since the account opened. Copying the details from a recent invoice rather than from memory removes most of this friction.
What it does not do
Signing an LOA does not cancel your existing service, commit you to a date, or start billing. It authorises a request. The port itself is scheduled separately once the losing carrier accepts, which is also when you should plan any cutover work.
Who has to sign it
The LOA has to be signed by someone authorised on the account with the losing carrier, which is not always the person managing the migration. In smaller businesses the account is often in a founder's name, or in the name of whoever set up the office years ago. Establishing who that is at the start, rather than after a rejection, removes the most common source of delay. If the authorised person has left the organisation, the account details have to be updated with the losing carrier first.