Just an update that I have received a message (interestingly, a direct email rather than a secure message on the TIAA-CREF page), that at least is a bit more considered than the rote "blah, blah, blah, 30%, tough luck" messages we all seem to have been given.
I will paste it below, identities removed, just as an FYI for everyone.
[bottom line is that the outcome still seems to be the same but at least it was a longer response and actually referred to aspects of tax law and the treaty).
"Dear Mr. XXX:
I am responding to your email dated November 4, 2016, in reply to an email sent by TIAA on November 3rd from Mr. XXX XXX, Customer Resolution Manager. Mr. XXX's email commented on the taxation of payments made to a non-US citizen residing in the United Kingdom.
A key issue at hand is the distinction between how periodic and non-periodic payments are treated under the U.S. – United Kingdom Income Tax Treaty. Since you are not a U.S. citizen and reside in the UK, your payments are subject to Non-Resident Alien (NRA) taxation. Internal Revenue Code Section 1441 and the regulations there under provide for withholding when a payment is made to a foreign person. Generally, payments made to a foreign person are taxed at 30%. However, under Regulation Section 1.1441-6(a), a foreign person may claim a reduced rate of withholding to the extent that it is provided for under an income tax treaty in effect between the United States and a foreign country.
It is our understanding the U.S.- United Kingdom Income Tax Treaty is currently in effect and pension distributions are covered under Article 18 – Pension and Annuities. The provisions under this article state that pensions may be taxed in the State (U.S.) in which they arise and according to the laws of the State (U.S.), but if the beneficial owner receives a periodic pension payment then the treaty provides a reduced rate of withholding of 15%. Simply, a foreign person who is a beneficial owner can receive either a lump sum pension distribution (e.g., a single cash payment or systematic withdrawals) or a periodic distribution (e.g., annuity income). The treaty only provides a reduced rate of withholding for periodic pensions, thus lump sum distributions will be taxed at 30% as provided for in Section 1441.
Your Retirement Annuity (RA) contracts provide the option to receive lifetime annuity income. However, in order to receive lifetime annuity income payments, you must make an irrevocable decision to convert a given accumulation to a payout contract that provides lifetime payments, periodic payments, under specific actuarial assumptions.
Allow me to elaborate on our position, counsel has found that when a treaty is silent on the definition of periodic and non-periodic payments (as the U.S.- UK treaty is), it reverts back to the country of source (where the payments originated) to make this determination. Since the treaty does not specifically define “periodic payment,” we are correct in our interpretation that lump sum payments are non-periodic and we therefore do withhold 30% from these payments.
We regret inconvenience you may have experienced in this matter. However, we have determined after careful consideration and research that our current position is in accordance with the applicable statutes governing this issue. Although previously suggested, if further clarification is needed - any general and or specific questions should be directed to a tax professional.
Sincerely,
XXXX XXXX
Customer Resolution Manager / Customer Care Team"