I'm using my taxpayer ID as my User ID, and it's telling me that I have an invalid username. How can this be if I used to login to the old system with it?

Each LaTAP user has a unique User ID to access LaTAP. If there is more than one LaTAP user for a single taxpayer, only one of these users can use the taxpayer ID for their user ID. If you used the old system, then your User ID may have been changed for use in LaTAP. For example if it was 9999999001, it may now be 9999999001-1. You should have received notification of this change, including the new User ID that will grant you TAP access. If you have not received this notification, please contact the Department of Revenue via email at Business Taxpayer Access Point(TAP) Inquiries or call (225) 219-2203.