There are different opinions on this (PFIC reporting within SIPPs). Whenever there is a difference of opinion I choose the one that indicates I don't have to pay any tax or preparation fees.
In addition to the link I posted easier, this:
https://help.taxesforexpats.com/article/537-uk-isa-sipp-foreign-trusts-on-us-tax-returnsays this:
<<
SIPPs are trusts to the same extent that every retirement account is a trust by nature.
<<
SIPP are not foreign trusts - beware of redundant formsBecause of the U.K.-U.S. treaty, SIPPs are considered IRS-qualified pension accounts. Therefore, there is no need to report them as foreign trusts. Income in SIPPs can be deferred just like income in a U.S. IRA accounts.
We are often asked this question (is my SIPP a foreign grantor trust), as other tax preparers (often in the U.K) are notorious for preparation of redundant forms to justify high fees they charge for US tax returns. Ironically, along with forms 3520-a they commonly file form 8833 explaining that US retirement plans are IRS-qualified, although it has been determined that this obvious fact does not need treaty-position disclosure.>>
With regard to 8261, from here:
https://www.pwc.com/gx/en/services/people-organisation/publications/assets/pwc-united-states-pfic-guidance-provides-new-reporting-exceptions.pdf<<
The temporary PFIC regulations
provided an exception for certain
foreign pension funds. Specifically, no
Form 8621 must be filed for PFIC
interests that are owned through a
foreign trust that is a foreign pension
fund operated principally to provide
pension or retirement benefits where
an income tax treaty essentially
provides that the earnings from the
pension fund are not taxable until
distribution. Effectively, this
exception only applied to those
foreign pension funds treated as
foreign trusts under entity
classification rules for US tax
purposes.
The final regulations expand this
exception to include all applicable
foreign pension funds (or equivalents)
under any type of arrangement
regardless of their classification for
US federal tax purposes. This
exception applies for any beneficiary
of, participant in, a plan, trust,
scheme, or other arrangement that is
treated as a foreign pension fund if an
income tax treaty states that any
income from the fund is only taxed
when it is paid to the shareholder. >>
So the gains grow tax free until withdrawn. At withdrawal time you may or may not have a basis in the pension ( I believe this depends on whether you funded it personally, or your employer funded it). If you have a basis you would be taxed only on the profit. Take those payments periodically and allocate the profits (which are taxable) to the 25% you get tax free.
Income from the SIPP will accrue WEP on your US social security - unless you liquidate the SIPP before taking US SS (which I plan to do).
A