Form 8621 for SIP investors: why 100+ lots matter and how excess distributions are computed
Not tax advice. The example below is illustrative. Your preparer may make different method choices (FX conversion, holding-period start, rounding). Preparer review is required.
Why a SIP creates so many lots
A systematic investment plan buys units every month. Each purchase is a separate block of shares with its own purchase date and cost. Under §1291 the excess distribution is spread "ratably to each day in the taxpayer's holding period for the stock."[1] Blocks bought on different dates have different holding periods, so practitioners generally compute each block (lot) separately. Ten years of monthly SIPs in one fund is 120 lots. Five funds is 600. Redemptions are usually matched against lots first-in, first-out (confirm the ordering method with your preparer), so one redemption can touch dozens of lots, each with its own year-by-year allocation.
Generic PFIC calculators require keying each lot by hand. That is why preparers often bill §1291 work hourly.
The §1291 steps, per lot
- Find the excess distribution. On a redemption, all gain (proceeds minus basis, in USD) is excess. For cash distributions, the excess is the part above 125% of the prior three years' average.[1][2] Indian growth-option funds usually pay no distributions, so redemptions drive the result.
- Count holding days and allocate the excess evenly by day to each tax year in the holding period.
- Current year and pre-PFIC days (for example, days before you became a US person, subject to your preparer's analysis): these amounts are ordinary income on your return.[1]
- Each earlier PFIC year: multiply the amount by that year's highest individual rate (37% for 2018–2025) to get the deferred tax.[1][3]
- Interest: charge underpayment interest on each deferred tax from the original due date of that year's return to the due date of the current year's return. The rate is the federal short-term rate + 3 points, set quarterly and compounded daily.[1][4]
- Sum across lots and funds. The totals feed Form 8621 Part V (line 16) and flow to your Form 1040 as additional tax and interest.[2]
Worked example
Facts (USD amounts, already converted; one fund; a calendar-year US person throughout):
- Lot A: bought 2023-01-01 for $1,000, redeemed 2025-12-31 for $1,600. Gain = $600.
- Lot B: bought 2025-06-01 for $1,000, redeemed 2025-12-31 for $1,050. Gain = $50.
- Holding days are counted from the day after purchase through the redemption date. 2025 is the current year, and there were no prior distributions.
Lot A: allocation
Days: 2023 = 364 (Jan 2 to Dec 31), 2024 = 366 (leap year), 2025 = 365. Total = 1,095.
| Year | Days | Allocation = $600 × days / 1,095 | Treatment | Deferred tax (37%) | Interest to 2026-04-15* |
|---|---|---|---|---|---|
| 2023 | 364 | $199.45 | Prior PFIC year | $73.80 | $11.65 |
| 2024 | 366 | $200.55 | Prior PFIC year | $74.20 | $5.35 |
| 2025 | 365 | $200.00 | Ordinary income, current year | — | — |
| Total | 1,095 | $600.00 | $148.00 | $17.00 |
Hand check: 600 × 364 / 1,095 = 199.45; 600 × 366 / 1,095 = 200.55; 600 × 365 / 1,095 = 200.00; the three add back to $600. 199.45 × 0.37 = 73.80 and 200.55 × 0.37 = 74.20.
*Interest is compounded daily at the IRS individual underpayment rates for each quarter. Rates applied: 8% for 2024 Q2–Q4, 7% for all of 2025 and 2026 Q1, 6% for 2026 Q2. The 2023-year tax runs from 2024-04-15 to 2026-04-15. The 2024-year tax runs from 2025-04-15 to 2026-04-15.[4] Sanity check: $74.20 at 7% compounded daily for one year ≈ $5.38, and the last two weeks at 6% trim it to $5.35. $73.80 at about 8% for 8.5 months and then 7% ≈ $11.65. Figures are rounded to cents. Actual returns round to whole dollars.
Lot B
All 213 holding days fall in 2025, the current year, so the $50 is ordinary income, with no deferred tax and no interest.
Result for this fund
- Ordinary income (current year): $200.00 + $50.00 = $250.00 (taxed at your 2025 marginal rate).
- Deferred tax: $148.00. Interest: $17.00.
With only two lots this is easy. With 120 SIP lots, each redemption repeats the table for every lot it consumes, with different day counts, several years and different interest periods. The method mirrors the IRS SB/SE PFIC training exercises: daily allocation, the highest rate for each prior year, and §6621 interest. PFIC Ledger's engine is tested against that training answer key to the dollar.
Edge cases your preparer will ask about
- Currency. Basis and proceeds should be translated to USD. Methods (spot rate on each date vs. alternatives) affect the gain.
- Pre-US-residency days. Days in a lot's holding period before the fund was a PFIC as to you can be ordinary income rather than deferred-tax years. How that applies to your arrival date is a preparer judgment.
- Switches and STP transfers between schemes are redemptions of the source scheme.
- Prior filings. Earlier elections, or 8621s not filed, change the starting point.
Sources
- 26 U.S.C. §1291: law.cornell.edu/uscode/text/26/1291
- IRS, Instructions for Form 8621: irs.gov/instructions/i8621
- IRS, Tax inflation adjustments for tax year 2024 (top rate 37%): irs.gov/newsroom/irs-provides-tax-inflation-adjustments-for-tax-year-2024; 26 U.S.C. §1(j): law.cornell.edu/uscode/text/26/1
- IRS, Quarterly interest rates: irs.gov/payments/quarterly-interest-rates; 26 U.S.C. §6621: law.cornell.edu/uscode/text/26/6621
- IRS SB/SE PFIC workshop exercises (Section 1291 examples, as reproduced by a practitioner): bragertaxlaw.com/files/sbse_doc_%20154.pdf
Disclaimer: This article was published by Ripplarity Inc (PFIC Ledger) for general information. It is not tax, legal or accounting advice and does not create a preparer or advisory relationship. The numbers are illustrative. Preparer review is required before filing.