After-tax 401(k) is the appropriate name while "Mega Backdoor Roth" is an equivalent term coined by White Coat Investor and documented in this forum thread: The Mega Backdoor Roth IRAdafioram wrote: ↑Thu Jun 03, 2021 6:51 pm 2. How about we change https://www.bogleheads.org/wiki/After-tax_401(k) to be "Mega Backdoor Roth" as the title? Mega Backdoor is a special case of after-tax and I think after-tax can also apply to other things such as variable deferred annuities (which go in after-tax for non-qualified). We could have a page just for after-tax which compares it against taxable investing as one example as to after-tax being a separate thing from mega backdoor.
Is there a difference between them?