IBKR Dividend Tax Calculator (PIT-38)

Disclaimer: the figures shown here are for reference only and may not represent your actual tax liability. Tax law is complex; individual circumstances vary. Always verify all calculations yourself and consult a qualified tax adviser before filing. The author accepts no responsibility whatsoever for errors, omissions, or any consequences arising from reliance on this tool. This project is not affiliated with, endorsed by, or in any way connected to Interactive Brokers LLC or the Polish tax authority (KAS). "IBKR" and "Interactive Brokers" are trademarks of Interactive Brokers LLC. All references are purely descriptive.

How calculations work The calculator reads DividendDetail / Summary rows from the IBKR annual activity CSV — one row per payment date per ticker. Revenue component rows are ignored to avoid double-counting.

For each payment:

Gross PLN: gross dividend in USD × NBP table A mid rate, rounded to 2 decimal places
NBP rate date: last business day before the payment date (ReportDate), per art. 11a ustawy o PIT; if that day is a public holiday the calculator walks back up to 7 days
Tax 19% (poz. 47): Gross PLN rounded to the nearest whole złoty × 19% — income is declared in whole PLN on PIT forms
Paid (poz. 48): actual Withhold amount from the CSV Summary row × NBP rate; withheld % of gross shown in brackets
Left (poz. 49): poz. 47 − poz. 48 — what remains to pay in Poland; % of gross shown in brackets

Totals in poz. 47–49 are additionally rounded to whole złotys as required by the form.

W-8BEN and withholding rate The standard US withholding rate for foreign investors is 30%. Under the US-Poland tax treaty (art. 10, Convention signed 1974) this is reduced to 15%, but only when a valid W-8BEN form is on file with your broker. Interactive Brokers collects W-8BEN during account opening for all non-US clients and re-collects it every 3 years; if it lapses, IBKR reverts to 30% without notice. The withheld percentage is calculated from your CSV and shown in brackets in the Paid column — if you see 30% there, your W-8BEN may have lapsed.

Note: this calculator currently supports USD dividends only (US stocks via IBKR).

If withheld at 30% — PIT-38 fields 47 & 48 Polish law (art. 30a ust. 9 ustawy o PIT) lets you credit foreign tax paid against the Polish 19% due, but the credit is capped at the Polish tax calculated:

poz. 47: Polish tax due — 19% of gross income in PLN
poz. 48: Foreign tax paid, converted to PLN — cannot exceed poz. 47

If you were withheld at 30%, you can only credit up to the 19% from poz. 47. The excess 11% is not refundable by Poland — you would need to reclaim it from the US IRS (Form 1040-NR), which is complex. This is why keeping W-8BEN current matters: with 15% withheld, you simply pay the remaining 4% to Poland.