you use up your MA basis (contributions as an MA resident) if and as such distributions are not taxed by MA, if you were not a lifelong MA resident, some contributions might not be MA basis.
once you use up your basis, the rest is earnings in your IRA and you will be taxed on it.
As I recall MA does not prorate the basis and earnings each year, like IRS does.
"previously taxed" means taxed on a MA return you filed prior to the tax year you are filing now.
There should be no confusion.
We're all on the honor system here.
