If you see an error saying that your authorization code is invalid when you try to initiate your domain transfer, you may have simply typed one or more characters incorrectly.
Try retyping your code again. If you're copying and pasting the code from another page or document, make sure you didn't accidentally leave out or add any characters, or include a blank space before or after the code.
If your authorization code still doesn't work, please contact your registrar for assistance. Your registrar may be able to help determine why your authorization code could be failing.
Tip: Don't remember which registrar you used? Look it up.