It will not let you file? For 2023? You cannot e-file a 2023 tax return now in December. 2023 is not over until December 31, 2023, and the IRS will not begin to accept e-files until sometime in mid to late January.
How could you be ready to file? Employers have until the end of January 2024 to issue W-2's, businesses, banks and financial institutions will not issue 1099's until late January/early February.
You need ALL of your tax documents in order to file. You will have to wait at least another month before you can file a 2023 tax return, and even then, do not file unless you have all of your documents. They all have to go on the same tax Form 1040.
If you are asking about filing for a different tax year---you cannot use online for any other tax year. It is only for 2023 returns. And if you are trying to file for an earlier year like 2021 or 2022, you have to use the CD/download software, and your return cannot be e-filed. It has to be sent in the mail.