Here is a sentence for you:
The Amiga Computer Corporation has finally closed its doors
permanently as of January 2018.
Should the comma(s) be placed like this:
The Amiga Computer Corporation has finally closed its doors
permanently, as of January 2018.
OR
The Amiga Computer Corporation has finally closed its doors
permanently, as of January, 2018.
OR
… No commas used at all?
Best Answer
The rule is that no comma is required between a month and a year if there is no number between them. (This rule is widely cited. See, e.g.: https://owl.english.purdue.edu/owl/owlprint/607/.)
When, as in your example, a date is at the end of a sentence, no comma is required before the date. (See, e.g. grammartips.homestead.com; “When to Use Commas with Dates”)
The sentence is, in any case, a bit awkward. The use of the past perfect (has...closed) indicates a completed action in the past while the date, January 2018, is still in the future. If the date is in the future the sentence should read: "The Amiga Computer Corporation will finally close its doors permanently (note spelling) in January 2018." If the closing occurred in the past: "The Amiga Computer Corporation finally closed its doors permanently in January 2017." The use of "as of" is also problematic. It is best employed to indicate the effective date of an action or document which has been or will be executed at some different time (or times, in the case of multiple actors). When this nuance is not present, "as of" should be eschewed in favor of "on" or "in". See Garner's Modern English Language, Page 75.