Once you are issued an SSN, use it when paying your estimated taxes. Use your SSN when paying your estimated taxes even if your SSN does not authorize employment or if you have been issued an SSN that authorizes employment and you lose your employment authorization. An ITIN will not be issued to you once you have been issued an SSN. If you received your SSN after previously using an ITIN, stop using your ITIN. Use your SSN instead.