InternetJeff
I don't even wait for my 1099s to come out. Since mine is from both stock income and 401k withdrawals, it was pretty easy to get all of my information.
With my Employee stock, I can refer to my stock confirmations. I list all of my stock transactions one by one. Takes little time entering it all but I can make sure it's 100% right.
Same thing with the employee stock. If I need a reference, then I can look at the year's before. I can also pull up the total amount of the 401k withdrawal as well, and fill out the appropriate information.
I been doing this since 2015 with my current employer. Once Tax season opens up, I start entering all of the information. I can also figure out my W2 numbers except for the SS wages since they are always higher due to the way they do our health insurance.
So I will take that information from my last check of each year and make a temporary W-2 for my employer. It gives me an estimate of what my refund will be. I will then update my W2 once it is released. Usually around Jan 16, 17th.
Of course it won't be processed until at least February 15th due to the EITC