After successful completion of the ISO 9001 lead auditor training, you can be a qualified auditor for third-party auditing.
You can be a part of the IRCA by registering yourself there.
As a lead auditor, you are qualified to issue certificates to internal auditors.
Moreover, you don’t have to keep renewing your certificate as an auditor by taking up an auditor training on a regular basis. You will be required to do it only when the standards are revised.