Kaptal

The numbers your broker won't give you

Nine tax calculators for cross-border investors, each aimed at a figure that exists in law but not in any portfolio tracker.

Every one of these tools computes something an incumbent could build but doesn't. The reason is the same each time: they don't trust their own data enough to print a tax number. One competitor resets cost basis to €1 on a broker transfer; another shows +7.28 % on the web and −2.74 % in its own app for the same portfolio. You cannot put a tax figure on that. Correctness is the product — these calculators are the proof.

Deadline-driven

New law — everyone starts from zero
🇵🇱 Poland 1 Jan 2027

Kalkulator OKI

Compares the new Osobiste Konto Inwestycyjne against IKE, IKZE and a plain brokerage account — including the trap that VWCE, IWDA and CSPX do not qualify.

Gap: The one existing OKI tool compares wrappers but will not optimise the split.

🇩🇪 Germany 4 Jan 2027

Vorabpauschale-Rechner

What your broker will debit in January, worked step by step — Basiszins at its all-time high of 3.20 %, capped at real growth, with Teilfreistellung and Freistellungsauftrag applied.

Gap: Only one competitor computes it at all, and none emits a filing.

Currency, separated from performance

The one number no broker statement contains
🌍 Cross-border Thesis

FX Cost Basis

Converts both legs of a trade at their own dates and splits the taxable gain into the part the asset earned and the part the currency did — including the case where a position sold at a loss is still taxed.

Gap: No competing calculator ranks for this at all; the incumbents are forum threads.

🇵🇱 Poland PIT-38

Kurs NBP do PIT-38

The same split under Polish rules: NBP average rate from the business day before each leg, fees riding with their own leg, and the D-1 reference date worked out for you.

Gap: Filing services compute the total. None shows how much of it was the złoty.

Structurally unserved

The incumbent publicly declines to compute it
🇳🇱 Netherlands Flagship

Werkelijk rendement box 3

Other tools ask you to type in your actual return. This one derives it — income plus realised and unrealised change, corrected for deposits — and shows whether tegenbewijs beats the forfait.

Gap: DEGIRO's own helpdesk page says it will not calculate this for you.

🇨🇭 Switzerland Time-boxed

Säule 3a Nachzahlung

Which contribution gaps can still be closed, what each costs, and what it saves at your marginal rate. 2026 is the first year the rule is usable at all.

Gap: finpension states in its own guide that multi-provider holders cannot get this data.

🇸🇬 Singapore Flagship

SRS Withdrawal Planner

Ten-year staggered drawdown across the resident brackets — plus the foreigner case, where one irreversible withdrawal and a ten-year residency clock decide whether the 5 % penalty applies.

Gap: No government SRS calculator exists — not at CPF, not at MOF.

🇺🇸 UAE · Singapore · global Expat

US Estate Tax Exposure

What your heirs would owe the IRS on US-domiciled holdings above the $60,000 threshold, and the same money modelled as Irish UCITS — including the PFIC inversion for Americans abroad.

Gap: Robo-advisors write articles about it; nobody ships the calculator.

🇩🇪 Germany Multi-broker

Freistellungsauftrag-Rechner

One allowance, many brokers. Flags over-allocation, which is unlawful and reported centrally, and under-allocation, which quietly costs you money until you reclaim it a year later.

Gap: No single bank can see the others — structurally our problem to solve.

The writing behind them

Each figure sourced and dated

🇵🇱 Poradnik inwestora

OKI, IKE, IKZE i PIT-38 z zagranicznym brokerem — po polsku.

🇳🇱 Uitleg box 3

Werkelijk rendement, tegenbewijs en de overgang naar 2028 — in het Nederlands.

🌍 Cross-border guides

FX cost basis and US estate tax exposure, for investors who hold accounts in several countries.

Prototypes, August 2026. Every figure is an estimate for orientation, never tax advice — each page carries its own disclaimer. Formulas were verified against primary sources (BMF, BVI, Belastingdienst guidance, BVV 3, IRAS, IRS Form 706, NBP table A) at build time; rates change annually and need a yearly review before publication. The Polish OKI figures still rest on secondary sources — they need checking against the enacted text before this goes live.