Form 8621 · §1291
The Form 8621 §1291 calculation, explained
How the default 'excess distribution' regime works — allocation across the holding period, the top-rate tax, and the interest charge — with a worked example.
By Danilson Ramos · Founder, Atamatax
Published July 2026 · Updated September 2026
Check it for your own holding
Could this investment be a PFIC?
Two questions and, if you have it, the ticker or ISIN. The read is immediate, nothing you enter leaves this page, and it names what would settle the rest.
Free, no account, nothing you answer leaves this page. Open the full portfolio scanner
Screened against the fund registry on this page. It is never sent anywhere.
A screen. Whether a fund is a PFIC turns on its own annual income and asset facts under §1297; the read above says how far your answers go and what would settle the rest.
The §1291 regime applies when you make no election, and it's the punitive one. Here's how the calculation actually works.
Step 1 — identify the 'excess distribution' (or gain)
An excess distribution is broadly the part of the year's distributions above 125% of the average of the prior three years; a gain on disposition of PFIC stock is treated similarly. The current-year portion is taxed normally — the rest is 'thrown back'.
Step 2 — allocate ratably across your holding period
The throwback amount is spread evenly across each day you held the PFIC.
Step 3 — tax the prior-year portions at the highest rate, plus interest
- Amounts allocated to prior years are taxed at the highest ordinary rate in effect for each of those years.
- An interest charge (like an underpayment charge) is added, dated back to those years.
- The current-year portion is taxed as ordinary income this year.
Worked example
Build it on your own numbers: enter the gain or distribution and your holding period, and the calculator produces the allocation, the back-tax, and the interest charge.
Run the §1291 numbers
Build the worksheet on your figures. This is general information, not individualised tax advice.
From one fund to the whole case
What does your PFIC situation actually require?
Four questions — how many funds, for how long, whether Forms 8621 were ever filed, whether the returns are current — and a route into the preparation that fits, with what it costs. Nothing you answer leaves this page.
Free, no account, nothing you answer leaves this page. Open the full portfolio scanner
A routing read, not a determination. Whether a fund is a PFIC, whether an exception applies and what a prior year needs are established when the holdings are screened; the route above says where that happens and what it costs.
Authorities cited
- IRC §1297 — IRC §1297 — Definition of a passive foreign investment company
- IRS Form 8621 — About Form 8621 — Information Return by a Shareholder of a PFIC or QEF
- IRC §1291 — IRC §1291 — Interest on tax deferral (excess-distribution regime)
Primary sources (Cornell Legal Information Institute for the US Code and CFR; IRS.gov for forms, procedures, and treaty documents). This page is general information, not individualized tax or legal advice.
Atamatax provides tax preparation support and educational resources. This website does not constitute legal or tax advice.