I came across your post because I was searching for the same answers.
What I could find was USCIS and IRS have different definitions for resident aliens. Since Upwork requires this information to be filled on their Tax Information page, I assume that the definitions as per IRS should be taken into account in this particular situation. If you read the definition of US person + Resident Alien + Substantial Presence all together from the IRS website things might get more clearer.
As per the IRS website:
The term "United States person" means:
Additionally they define resident alien as
Substantial Presence test:
You will be considered a United States resident for tax purposes if you meet the substantial presence test for the calendar year. To meet this test, you must be physically present in the United States (U.S.) on at least:
Sorry I forgot to update this poset - someone from UpWork has reached out to me through a ticket and told me where to change in my settings in order to have access to the right tax form. (If you need the instruction as well feel free to PM me.) I have not done so since I haven't got a contract anyway, but the person from UpWork support team told me that doing that will allow me to fill the right tax form without loss of access to US-only jobs.
And I'm aware of the information you copied there - but I don't think it's up to us users to "assume" which definition UpWork follows. UpWork has a definition which they show you when you choose between "US person" and "non-US person". I'm very clear that I'm a non-residnet alien (because F-1 visa holders are exempt from the substantial presence test for 5 years and this is my 5th year in the US) as per IRS's definition. But choosing "non-US person" on my account will 1. prevent me from accessing all the "US-only" jobs and 2. mean that I'm ignoring UpWork's explicit definition of "US person" and substituting that with IRS's version. I didn't want to ignore instructions from UpWork unless explicitly told by UpWork's support team.
I'm pasting below parts of the answer I received from UpWork Customer Support through a Request. (Mods - please delete/edit if this is not allowed.) I have not tried the solution suggested by the Support staff yet as I haven't been active on UpWork lately.
"by default, when a user uses a US Address, the system will prompt to enter their W-9 information. If you need to fill out W-8BEN, you need to use your permanent residence address to enable W-8BEN. Once changed, you can fill out W-8BEN. You can access your Settings change to change the address/Country.
1. If I change my address to my home/permanent address, does that mean I will no longer have access to “US only” jobs?
Thanks for your question. This new feature is designed for clients who have a specific need for a freelancer in their country (reasons vary, but in many cases they need the possibility of on-site coordination, localized knowledge, or have to meet certain compliance rules for their company). However, our location confirmation process allows for periodic travel, so if we’ve been able to confirm you are in the U.S. you’ll still be able to submit proposals for jobs where the client is requesting U.S. freelancers only. It will then be up to you and your client to determine whether your travel schedule affects your ability to meet their job requirements.
2. My tax residency status will change from non-resident to resident on Jan 1st 2019, meaning at that point my appropriate tax document changes from W-8BEN to W-9. Are you suggesting that I should change my country now, and then change it again back to the US when 2019 comes?
Yes you can do that. You can change your address bank to United States when you already have the residency or permanently be staying in the US."
Hope this helps.