I'm glad you raised this concern here, @EYDO. 

I'll share info about entering a Tax Identification Number (TIN) in QuickBooks Online (QBO) Tanzania.

There's an acceptable format for TIN in QBO Tanzania, a 9-digit arrangement wherein 8 numeric +1 alphanumeric numbers. Examples are 12-123456-A, 12123456-A, and 12123456A.

If you follow these formats and the issue persists, let's perform some basic troubleshooting steps to fix this. We can start by accessing your QBO account in a private/incognito browsing window. This will determine if it's a browser-related concern because cache files won't be saved here. 

Feel free to utilize these shortcut keys:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Microsoft Edge: press Ctrl + Shift + N
• Safari: press Command + Shift + N

From there, enter your TIN following the correct format. Once it works well, go back to your default browser. Then, initiate a clear cache to remove outdated files. If the issue persists, we can use another supported browser. This happens if the one you're currently working on has a temporary issue with QuickBooks.

After performing the steps, if the same error happens, I recommend contacting the QBO Care Team to review your account and find a solution.

If you want to see a detailed look at your owed taxes, check out this article: Check how much sales tax you owe in QuickBooks Online.

For additional questions about managing your tax info, leave a comment below. We'll be willing to help. Keep safe, and have a good one.