"in same year"

Meaning they made a nondeductible contribution to the Traditional IRA before 2020 year end and converted that to Roth before 2020 year end, as well.

Or, it's not "same year" because they contributed for 2020, in 2021 (as allowed per the due date of the tax return), and then converted in 2021, which makes that conversion reportable as 2021.

For not same year:

If your client made a backdoor Roth, which is a conversion of a nondeductible Traditional IRA contribution to a Roth, with the client having no per-tax or deferred funds in any other similar deferred account type per the IRS, and that means that what they converted there was also only Basis with no earnings, there would be no taxable income to report in 2021.

And for 2020 you have a nondeductible, post-tax, contribution. "Already Taxed" in MA.

Go here and scroll down to the Roth section:

https://www.mass.gov/service-details/view-non-government-pensions