What we build
8621 Calculator supports §1291 excess distribution and §1296 mark-to-market calculations. It turns CSV transaction histories into Excel workpapers, with lot-level calculations and Form 8621 supporting statements that users can review.
Access is US$10 per PFIC calculation, with no subscription. The service provides calculations and workpapers; it does not determine PFIC status, choose elections or file your return.
Read the scope and assumptions →Who maintains it
Hans is the creator and maintainer of 8621 Calculator and PFIC Report, focused on translating PFIC calculation rules into reproducible software workflows.
Hans is a technical builder, not a CPA or Enrolled Agent. The software supports tax professionals and technically capable DIY filers who can review their inputs and outputs.
Read more about Hans at PFIC Report →Research and open-source tools
These resources share a creator and serve different parts of the calculation and review process.
PFIC Report
PFIC Report is the companion research and educational website maintained by the same creator. It provides worked examples, country-specific analysis and Form 8621 calculation guides.
It explains the methods and context behind the software. It is an affiliated resource, not an independent certification of the calculator.
Explore PFIC Report →IRS §6621 Interest Calculator
The standalone interest calculator is open source. Its HTML, JavaScript and CSS are available on GitHub for inspection and use under the MIT License.
The full PFIC calculation engine is proprietary. The open-source tool lets users inspect interest calculations; it does not by itself validate every part of a PFIC calculation.
How to evaluate the calculations
Review methods, sample outputs and worked examples alongside user feedback.
Methods & Verification
Inspect allocation, currency conversion and interest methodology, with links to the relevant IRS authorities.
Accuracy & Verification →Inputs & Workpapers
See the CSV workflow and downloadable sample workpapers for §1291 and §1296 calculations.
View workflow & samples →User Feedback & Cases
Read supporter messages, Reddit discussions and direct submissions, then explore three worked cases.
Read User Feedback →Contact
For technical support, access questions, feedback or a reproducible calculation issue, email support@8621calculator.com.
For calculation issues, describe the steps, tax year and expected versus observed result. Please do not email Social Security numbers, account numbers or unredacted tax documents.
For information about transaction processing and feedback submissions, see our Privacy Policy.