MTM (§1296) Form 8621 Calculation Guide

PFIC Calculator (8621calculator.com) — MTM (§1296) Form 8621 User Guide

This guide is for PFIC holdings reported under the mark-to-market rules of IRC §1296 for marketable stock. It explains how to prepare the MTM CSV (including year-end FMV data), map transaction categories, configure MTM-specific settings, run the calculation, and download Excel workpapers for Form 8621.

1. Who Should Use This MTM Guide

Use this guide if:

  • The PFIC is marketable stock and a valid MTM (§1296) election has been made.
  • You need to compute annual FMV-based ordinary income or loss for Form 8621 Part IV.
  • You are tracking Unreversed Net MTM Income (UNI) and basis adjustments over multiple years.

If there is no MTM or QEF election and you are under the default regime, please use the Section 1291 User Guide instead.

2. Prepare the CSV Transaction File (MTM)

Prepare one CSV UTF-8 file per PFIC.
Do not combine multiple PFIC holdings in a single file — this calculator is designed to process only one PFIC at a time.

Required columns (must match exactly):

  • Date — YYYY-MM-DD (Excel Date Format Guide)
  • Details — text only; must not contain commas, quotes, or line breaks
  • Units — numeric only; no thousands separators
  • Value — numeric only; no thousands separators or currency symbols
    (Total amount in the original currency)
Date Details Units Value
5/03/2020Contribution1000015000
15/05/2021Sold-12.433-29.68
12/03/2022Reinvestment19.0838422.83
31/12/2023fmv10068.81320018.53
31/12/2024fmv10068.81317079.56

Additional rules for MTM:

  • MTM calculations require at least one FMV row for each tax year — from the first MTM year through the filing tax year.
  • FMV rows must appear at the end of the transaction list, one row per calendar year.
  • The Details field must be exactly: fmv (lowercase, no extra words, spaces, or punctuation).
  • Each FMV row must include:
    • Units — total units held at year-end
    • Value — year-end FMV in the original currency
  • Use the orange-highlighted rows in the sample table as your template.
  • The calculator does not store or remember any data — every run must include full historical transactions from the first acquisition through the tax year.
  • All Sale / Disposition transactions must use a negative Units value. Any positive Units is treated as an increase.
  • If Units or Value is blank, fill it with 0.

3. Upload File

Click the upload area or drag your CSV file into the box. After uploading, the panel on the right will switch to the Transaction Type Mapping section automatically.

Supported format: CSV (UTF-8 only). If starting from Excel, save as CSV before uploading.

4. Category Mapping

The calculator will attempt to auto-identify categories based on the Details column, but every row must be reviewed and confirmed.

Available categories:

  • Purchase
  • Distribution
  • Reinvestment
  • Sale
  • Return of Capital
  • Cost Base Adjustment
  • Ignore (excluded from PFIC computation)
Transaction Category Options

One-page classification summary (decision logic)

Use the rules below to choose the correct Type for each transaction. Correct classification is essential for both MTM adjustments and any disposition components that must still follow FIFO.

Units Value Description (what it says on the statement) Type
> 0 > 0 Buy / Purchase / Subscription / Contribution Purchase
> 0 Any DRIP / Reinvest / Reinvestment / Dividend reinvested Reinvestment
< 0 Any Sell / Sale / Redemption / Switch-out Sale
= 0 > 0 Dividend / Distribution / Interest Distribution
= 0 Any ROC / Return of Capital Return of Capital
= 0 Any Basis adjustment (e.g. prior-year QEF / MTM adjustment) Cost Base Adjustment
Any Any Fees / Charges / NAV adjustment / Internal fund tax Ignore

Special Cases — “Ignore” and Manual Mapping View Ignore Classification Guide →

Entries marked with -- Select Type -- must be manually mapped.
All other auto-identified categories must be reviewed and confirmed item by item — only accurate categorization will produce accurate calculations.

Any transaction marked as Ignore is excluded entirely from the calculator. Ignore items must not affect MTM income, cost basis, or Form 8621 amounts.

5. Configure MTM Settings

When the uploaded CSV file contains FMV rows, the calculator automatically switches to MTM (§1296).

  • Tax Year — must be selected.
  • Currency — must be selected.
  • Ownership % — percent held by the owner.
  • MTM Start — required. Select the first tax year of MTM treatment.
MTM Settings Panel Example

When transitioning from §1291 to MTM (§1296), a purging election is required to eliminate prior §1291 taint via a deemed FMV disposition.
PFIC §1291→MTM purge transition guide

6. Run MTM (§1296) Calculation

Once categories are mapped and settings are confirmed, click Run PFIC Calculation.

Run MTM Calculation Example

7. License Verification

Enter your email and license code. The engine will not start until validated.

Send a screenshot of your support to get a code via email.

License Verification Window

8. Download Excel Results

Download immediately after calculation. No history is stored.

Download Results Button

9. MTM Output Sheets & Sample Workpapers

B. MTM (§1296) Outputs

  • MTM_Calculations — annual FMV and MTM calculations (Lines 10a–12).
  • 8621 MTM Filing Example — Part I, II, and IV mock-up.
  • CCH_1.21_Additional — Part 1 fund data.
  • CCH_6.2_ElectionC — Section 1296 MTM election worksheet.
  • CCH_6.3_Sale1296 — CCH worksheet for MTM-related sales.
  • Other IRS tax forms (1040, Sch 1, Sch D, etc.)

Related professional insights: