A self-employed family member accidentally contributed some money to their individual IRA that they meant to go to their SEP-IRA (Vanguard's UI can be confusing on this). That alone isn't a problem because they have the money to also make the intended contribution to the SEP-IRA.
The hitch is that their income is high enough that the individual IRA contribution is non-deductible (because of their participation in the SEP). Normally I'd suggest to just convert that non-ded contribution to a Roth.
But since it appears that individual IRAs and SEP-IRAs are lumped together (except for contribution source and limits) I'm wondering such a conversion will actually be mostly taxable because of the entirely pre-tax SEP-IRA balance.
So is that true? For purposes of Roth conversions of individual IRAs are SEP-IRAs considered an IRA and the SEP-IRA balance goes into the conversion taxability calculation? Or for purposes of Roth conversions are SEP-IRAs considered to be a separate thing that's excluded from the calculation (like solo 401ks are)?