Thanks @MarilynG1!
My W2 does attempt to split it out by state for me in the informational/summary section (i.e. outside of the boxes)
Within the boxes itself....
Box 16 of NJ reflects a fraction of taxable wages in line with the summary.
Box 16 of NY reflects whole year federal taxable wages (which I'm to understand is how New York requires it and is in-line with other posts in this chain).
But...From further reading:
Would I not be expected to use form NY IT-203-B Schedule A to do the allocation (as per NY Instructions for nonresidents) regardless of what my employer put on the informational summary section of the W2?
Basically NY IT-203-B Schedule A summarizes out to :
X "Workdays" working from home assigned to NJ office
Y "Workdays" working from home assigned to NY office
Y/(X+Y) = NY's % Allocation of taxable wages.
Further reading appears to suggest any year end discretionary pay (bonus) for 2020 but paid in 2021 should use a 2020 NY IT-203-B Schedule A allocation and not 2021's allocation (my W2 appears to agree in practice.)
For sanity sake:Tried to back into my employers numbers it appears they use a straight-line calculation via WEEKdays instead of WORKdays... which makes sense as they can't predict exactly when an employee will distribute future nonworking days in real-time and it's probably the best they can do.
X = "Weekdays" assigned to NJ office
Y = "Weekdays" assigned to NY office
Y/(X+Y) = NY Allocation
Every year I read way more about something personal tax related than I ever intended to :(
