The efile system has always stayed open for 5 days after the filing deadline for those rejected returns to make corrections and resubmit them. You will not be able to start a new online return after 10/16 ... you would need to use the downloaded version instead.
How long they keep the online system working after the 5 day perfection period is unknown ... last year they did keep it open until the end of October (not the norm) but as already said you can always mail in the return if efile has closed.
Now once the online system has been shut down access to the online returns will be locked out until the 2023 online program goes live sometime in early December so if you want a PDF of the return and/or the .taxfile so you can continue the return using the downloaded program then SAVE THEM NOW.
