Zinsklar: Compound Interest

German investment tax modeled properly: flat tax, allowance, partial exemption, advance lump sum and FIFO. Monte Carlo included. One time purchase, no subscription.

Zinsklar is the only calculator on the German App Store that models German investment taxation as one connected system: the flat capital gains tax (Abgeltungsteuer), the solidarity surcharge, church tax, the annual tax free allowance (Sparerpauschbetrag), the partial exemption for funds (Teilfreistellung) and the advance lump sum (Vorabpauschale). During drawdown it sells lot by lot in strict FIFO order, because German law leaves no choice.

Other calculators show a gross number. Zinsklar shows what the model leaves after tax.

THE TAX ENGINE • Flat capital gains tax plus solidarity surcharge, plus church tax at 8 or 9 percent depending on the federal state • Annual tax free allowance for a single filer or a jointly assessed couple • Partial exemption by fund type: equity, mixed, real estate, bonds • Advance lump sum with the official base rate of each year, fully credited against the later capital gain • FIFO during drawdown, every lot with its own cost basis and its own advance lump sum counter • Optional assessment at your personal income tax rate for years without wage income

WHAT YOU CAN CALCULATE • Your financial independence date: when the portfolio covers planned spending • Compound growth over decades, switchable between real and nominal • A savings rate entered directly or derived from income minus expenses • A year by year withdrawal plan including tax and inflation

MONTE CARLO Thousands of paths instead of one straight line, with a success probability and a percentile fan from P5 to P95. A historical block bootstrap shows what a bad sequence of returns does to a plan even when the average stays the same.

WITHDRAWAL STRATEGIES • Constant real or constant nominal • Fixed percentage of the portfolio • Guyton-Klinger guardrails • VPW, variable percentage withdrawal

LIFE PHASES Every phase carries its own return, savings rate and spending level, including a glide path. Part time work, parental leave, a sabbatical and the start of retirement can be modeled separately and compared side by side.

CONVENTIONS IN THE OPEN The methodology screen states how the math is done: contributions at the start or the end of the period, monthly compounding, returns as an effective annual rate, inflation discounted monthly, tax before inflation. Nothing is hidden and most of it is switchable.

ONE TIME PURCHASE, NO SUBSCRIPTION A calculator you open a few times a year does not belong in a weekly subscription. The full calculator including the complete German tax logic is free to use. Monte Carlo and withdrawal strategies unlock once and stay unlocked.

YOUR DATA STAYS ON THE DEVICE No account, no sign up, no bank connection, no server. Every calculation runs on your iPhone.

Zinsklar is a calculation tool, not investment, tax or legal advice. All results are model projections based on assumptions you choose yourself and are not a promise of future performance.