Basically a type of conversion, from Basis (nondeductible Traditional IRA) to Roth (which is always nondeductible).

And your client has to have No Other Basis or value in any Traditional IRA or tax deferred account, for this to work. Otherwise, you have a regular conversion with a taxable percentage.

Example:

They already have $5k in SEP-IRA. They put $5k into a Traditional IRA post-tax, and roll it to Roth as "backdoor" but what they did is take a 50% taxable distribution for conversion, indirectly.