Who to review 1099-r for 2020 income ref> no. on my stub was missing a number. need to review that 1099-r

Given that you have said "so far", I am guessing that you have not yet submitted your return for e-filing. Having said that, you can easily go back into the screen where you entered the information and double check it from there. If that is not correct and you have already submitted your return for e-filing, then most likely the IRS will reject the return because the information you submitted does not match what they have for you for this 1099-R (they receive this from the Institution that provided you with your 1099-R copy). However, the IRS is not beginning to accept e-filings for processing until February 12th 2021 for tax year 2020. So, if this is the case, you won't know until after that date.