Depending on the state you're in, sometimes you'll need the earlier return to calculate whether a state refund is taxable on the current return.  

I wouldn't enter anything under, say, tax history; I'd prefer that my client be able to distinguish between preparers and only want the data I prepared on the tax history form.  

I normally enter the prior year for new clients so I can use the two year comparison. I enter the prior year data on the "two year comparision worksheet" It's also a good exercise to check for any carry overs from the prior year to the current year. 

I always enter last year's AGI and tax for underpayment penalty computation purposes.

Where do I enter this information?  What if they did not have any income in prior year, therefore, did not file a tax return?  

Also, is anyone else having problems with the final review continually looping and never completing?  I have had basic returns with just W-2's, returns with W-2 and 1099-NEC, returns with W-2 and 1099-R - everyone I have done is not completing the final review (and these are from prior year transfers)?

Where do I input 2020 tax for underpayment penalty exception--I can't seem to find the proper input screen?

@Roseyfam   Federal Carryover Worksheet  Line 6