If E is a salesperson is it complicated because they’re bringing contracts to C in NY or because they might work on Commission?
[1]https://www.scotusblog.com/case-files/cases/new-hampshire-v-... [2]Which is already subject to sales tax after the reversal of the Quill Corp vs. North Dakota decision in South Dakota vs. Wayfair
ADDED: So I guess (although it's not super-clear) that it's a matter of being officially assigned to an office and maybe going in semi-regularly. Presumably if someone is 100% officially remote at a company with many offices, it wouldn't apply. https://andersen.com/pressroom/telecommuters-beware-of-state...
The you'd be surprised what certain states would say, do, and compose in their legal briefs to justify extracting as much money as possible.
Also IANAL, so take what I have to say with a grain of salt.
Presumably, there could be some kind of test. If someone lives in NH but is 100% WFH, he may be subject to MA income tax under the following standard:
1) If the company is headquartered or incorporated in MA
2) If the work done is provided (a) to directly benefit operations of aforementioned company that are affiliated with a location in MA or (b) to be sold/provided to third party legal person(s) for which business operations /purchasing/selling would be done in MA. (i.e a business/service nexus)
Otherwise, no. Most places in the U.S., you are treated as earning the income where you are actually physically located (i.e., your home residence).
In a nutshell, having an employee in a tax jurisdiction creates a taxable nexus for the company, meaning that they can be subject to income taxes, commercial taxes, sales taxes/VAT, etc., in that jurisdiction. (And note: this has been part of domestic and international tax law for decades.)
For example: Company C in CA has an employee, E, who moves to NY to work remotely. Company C is now subject to NY income taxes, and must now collect NY sales tax if they have any sales to NY customers (though note: in the US many states now require sales tax collection even in the absence of physical presence, so C may already have been obligated to collect NY sales tax). If E is a programmer, the NY income tax exposure is probably very low, but if E is in sales, they could be looking at significant NY tax liabilities based on how they may be required to apportion (aka allocate) their income between CA and NY.