How the forecaster works
The mechanics of the dividend snowball, and how to read the results honestly.
The snowball mechanic: how income compounds
Each year the model follows a specific sequence to grow your passive income:
- Calculate income: Current portfolio value × dividend yield = gross annual income.
- Apply tax: If using a "Taxable" wrapper, UK dividend tax is deducted (after the £500 allowance) to find your net income.
- Reinvest & Grow: Your net dividend income + fresh contributions are added to the portfolio, increasing the base that generates income for the following year.
This creates the "snowball" effect: your passive income starts small but accelerates as the reinvested capital compounds.
Why everything is shown in today's money
This calculator is nominal and shown in Today's Money: there is no inflation input. Your dividend yield is held constant and your expenses target stays flat, so you don't have to guess future inflation or read confusingly large numbers decades out.
Two caveats follow from this. First, income grows here purely because reinvested capital compounds; there's no separate share-price growth or dividend-growth term, which makes the snowball an optimistic, frictionless path. Second, in the real world both dividends and your living costs tend to rise over time: if they rose at exactly the same rate they would cancel and this view would hold in real terms, but that's an assumption, not something the model enforces. Read the crossover year as an approximate timeframe, not a precise date.
Reading the chart and results
Blue bars: Annual dividend income for each year — still building toward your target.
Green bars: Years where your dividend income equals or exceeds your target — financial independence achieved.
Dashed line: Your living expenses target. This is shown as a flat line because everything is modeled in today's money.
Progress bar: Shows your final-year income as a percentage of your target. 100%+ means your dividends have covered your life.
Assumptions and limitations
This model is a simplified projection for educational purposes. There are three deliberate simplifications, and they partially cancel each other out:
- Income grows only by reinvestment + contributions: there is no share-price growth or dividend-per-share growth term. In reality, companies tend to raise dividends over time and share prices climb, so your real income would likely grow faster than shown. This makes the crossover year conservative.
- Expenses are flat nominal: your living-cost target is held constant in today's money, but real expenses rise with inflation. Over a 30-year horizon that means the fixed target understates what you'll actually need, making the crossover look optimistic in real terms. The two biases, understated income growth and understated expense growth, partially offset each other.
- Dividends can be cut or suspended during market downturns, and your yield-on-cost will shift as you reinvest. The model uses a constant yield.
- Tax drag: For a taxable (GIA) wrapper the model applies the 2024/25 UK dividend regime: a £500 tax-free allowance, then 8.75% (basic), 33.75% (higher) or 39.35% (additional), which is held constant for the whole projection. The dividend allowance and tax bands assume a standalone position: if you have other dividend income pushing you into a higher band, your real tax will be higher.
The tool is best used to understand magnitudes and timeframes, rather than as a precise financial forecast. Read the crossover year as an approximate window, not a precise date.