A long-term investment model for a monthly VUAA (Vanguard S&P 500 UCITS ETF) contribution plan, projecting portfolio growth over 20 years and stress-testing it across ten different monthly deposit levels. It also models the Dutch Box 3 wealth tax: once the portfolio exceeds the tax-free exemption threshold, an annual tax applies on a government-assumed rate of return, separate from the actual market return.
At a €500 monthly contribution over 8 years, the plan turns €48,000 of principal into a projected €64,543 — a net gain of €16,543 — while the Box 3 wealth tax on the assumed return above the exemption threshold amounts to just €112, leaving €64,431 net.
Base case result — €500/month, 8 years
| Own contribution | €48,000 |
| Accumulated value (gross) | €64,543 |
| Net yield | €16,543 |
| Box 3 tax paid (36% on assumed 6% return above threshold) | €112 |
| Net accumulated value (after tax) | €64,431 |
At €500/month, compounding return pulls steadily ahead of principal — by year 20 the portfolio's growth component outweighs total contributions.
Portfolio Value vs. Own Contribution — €500/month, 20 years
The full two-variable data table — every combination of monthly deposit (€100–€1,000) and investment horizon (1–20 years) — showing projected portfolio value at each point. The €500/month row is highlighted.
Portfolio Value at Year 8, by Monthly Deposit
Full scenario grid — portfolio value (€)
| Monthly / Year | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| €100 | €1,240 | €2,572 | €4,003 | €5,539 | €7,189 | €8,961 | €10,864 | €12,909 | €15,104 | €17,462 | €19,994 | €22,714 | €25,635 | €28,772 | €32,141 | €35,759 | €39,646 | €43,819 | €48,302 | €53,117 |
| €200 | €2,480 | €5,144 | €8,005 | €11,078 | €14,378 | €17,922 | €21,729 | €25,817 | €30,208 | €34,923 | €39,988 | €45,427 | €51,269 | €57,543 | €64,282 | €71,519 | €79,291 | €87,639 | €96,604 | €106,233 |
| €300 | €3,721 | €7,716 | €12,008 | €16,617 | €21,567 | €26,883 | €32,593 | €38,726 | €45,312 | €52,385 | €59,982 | €68,141 | €76,904 | €86,315 | €96,423 | €107,278 | €118,937 | €131,458 | €144,906 | €159,350 |
| €400 | €4,961 | €10,288 | €16,010 | €22,156 | €28,756 | €35,845 | €43,458 | €51,634 | €60,416 | €69,847 | €79,976 | €90,855 | €102,538 | €115,087 | €128,563 | €143,037 | €158,582 | €175,278 | €193,209 | €212,466 |
| €500 | €6,201 | €12,861 | €20,013 | €27,695 | €35,945 | €44,806 | €54,322 | €64,543 | €75,520 | €87,309 | €99,970 | €113,568 | €128,173 | €143,858 | €160,704 | €178,797 | €198,228 | €219,097 | €241,511 | €265,583 |
| €600 | €7,441 | €15,433 | €24,016 | €33,234 | €43,134 | €53,767 | €65,187 | €77,451 | €90,623 | €104,770 | €119,964 | €136,282 | €153,808 | €172,630 | €192,845 | €214,556 | €237,874 | €262,917 | €289,813 | €318,699 |
| €700 | €8,681 | €18,005 | €28,018 | €38,773 | €50,323 | €62,728 | €76,051 | €90,360 | €105,727 | €122,232 | €139,958 | €158,996 | €179,442 | €201,402 | €224,986 | €250,316 | €277,519 | €306,736 | €338,115 | €371,816 |
| €800 | €9,921 | €20,577 | €32,021 | €44,312 | €57,512 | €71,689 | €86,915 | €103,268 | €120,831 | €139,694 | €159,952 | €181,709 | €205,077 | €230,173 | €257,127 | €286,075 | €317,165 | €350,556 | €386,417 | €424,932 |
| €900 | €11,162 | €23,149 | €36,024 | €49,851 | €64,701 | €80,650 | €97,780 | €116,177 | €135,935 | €157,156 | €179,946 | €204,423 | €230,711 | €258,945 | €289,268 | €321,834 | €356,811 | €394,375 | €434,719 | €478,049 |
| €1000 | €12,402 | €25,721 | €40,026 | €55,390 | €71,890 | €89,612 | €108,644 | €129,085 | €151,039 | €174,617 | €199,940 | €227,137 | €256,346 | €287,717 | €321,409 | €357,594 | €396,456 | €438,195 | €483,021 | €531,165 |
Rows = monthly deposit; columns = year. Figures are gross accumulated value (contribution + investment return) before Box 3 tax.