Simply put, "A Hawaii nonresident is an individual who is in Hawaii for a temporary or transient purpose, and whose permanent domicile is not Hawaii." (page 5 of Hawaii Nonresident and Part-Year Resident Income Tax Instructions - https://files.hawaii.gov/tax/forms/2019/n15ins.pdf).
Since I assume that you will work part of the year in Hawaii, you will be filing a part-year return IF you change your domicile when you leave for Germany.
So what is your domicile (for Hawaii purposes)?
"Domicile is the place of the individual's true, fixed, permanent home and principal establishment, and to which place the individual has the intention of returning whenever the individual is absent." (https://files.hawaii.gov/tax/legal/tir/1990_09/tir97-1.pdf)
"An individual's domicile may change where there is a concurrence of: (1) an abandonment of the old domicile with a specific intent to abandon the old domicile, (2) an intent to acquire a specific new domicile, and (3) an actual physical presence in the new domicile." (https://files.hawaii.gov/tax/legal/tir/1990_09/tir97-1.pdf)
That is, once you have established Hawaii as your domicile, Hawaii will remain your domicile until you take positive steps to establish a new domicile.
What might that mean?
"A change of domicile will depend upon the acts and declarations of the individual concerned in order to ascertain whether or not the individual possessed the required intention which the law says the individual must have to effect
a change of domicile. The status of an individual as a resident or nonresident is determined by all the factual circumstances. No single factor, such as an individual’s oral declarations of intention or the marriage of a resident and a nonresident, is controlling. Some of the relevant factors include the length of time spent in Hawaii; leasing, buying, negotiating for or building a home; ownership of a motor vehicle; place of issuance of license to drive a motor vehicle; place where the motor vehicle is registered; place of marriage; where the residence of one spouse is in issue, the place of residence of the other spouse; residence of the family of the individual; place of schools attended by the individual’s children; the presence of bank accounts; club memberships; place of voting; place of business interests, profession, or employment; contributions to local charities; declarations regarding residence made to public authorities, friends, relatives or employers, or in documents such as deeds, leases, mortgages, contracts, and insurance policies; proposed place of burial or acquisition of burial place for the individual or members of the individual’s family; and the place to probate a will." (https://files.hawaii.gov/tax/legal/tir/1990_09/tir97-1.pdf)
So, in summary, you will need to take steps to establish a new domicile in Germany, such as owning or renting a place to live, buying or leasing a German auto, getting a German drivers license, and perhaps most importantly, getting a German residence visa showing that you have the right to live there.
If you do this, you will no longer be considered a resident of Hawaii.
As I noted before, you will likely be considered a part-year resident of Hawaii: "Part-Year Resident
A part-year resident is an individual who was a Hawaii resident for part of the year, and who was a nonresident during the other part of the year. This includes those who moved to Hawaii during the year and those who moved
away from Hawaii during the year.
A part-year resident must file an Individual Income Tax Return—Nonresident and Part-Year Resident (Form N-15), if required to do so. A part-year resident will be taxed on all income from all sources during the period of residency, and on income from Hawaii sources only during the period of
nonresidency." (page 5 of Hawaii Nonresident and Part-Year Resident Income Tax Instructions - https://files.hawaii.gov/tax/forms/2019/n15ins.pdf)
So if I understand your situation correctly, you can tell your employer (or whomever) that you will no longer be a Hawaii resident for tax purposes...and save this answer in your tax files in case Hawaii ever asks you about it.
