My employer has invited me to use QB online they have 4 sets of QB online accounts. The email invite is to my one email address. How can I sign into the other accounts

Thanks for reaching out to the Community, @vbernstein-novat.

To sign in to the other company files, the Master Admin would have to invite you to each QuickBooks Online account. They can use the same email or User ID when they invite you so all of the companies are together. Next time you get invited, when you click on the accept invite link, it will ask you to sign in instead of creating new login credentials. To learn more about this process, please refer to this Community article: Add, delete, or change users.

Additionally, having the same email or User ID for QuickBooks will make it easier to rotate between companies. After signing in, you'll see the list of companies you can work in. Once you're finished with one company, just press on the Gear icon at the top-right of the page and select Switch company to the list once again. I've provided a screenshot below as a reference:

Furthermore, if you happen to have multiple login credentials, you can use this Community article to move them all to the same login: Sign in to multiple QuickBooks Online companies with one user ID.

Please let me know if there's anything else I can help you with by leaving a comment below. Have a great rest of your day!