Building a Tax-Aware Compounding Engine: Why Most Dividend Calculators are Mathematically Flawed Engineering a financial roadmap in 2026 requires more than a simple principal * (1 + r)^n formula. For high-net-worth investors managing assets across Charles Schwab , Fidelity , and Vanguard , the primary bottleneck is data integrity—specifically, the failure to model the tax drag that quietly erodes long-term compounding. Most "free" dividend calculators are mathematically irrelevant because they ignore the silent killer of wealth: Tax Liability . If your engine doesn't distinguish between Qualified and Ordinary dividends or account for state-level liabilities, your 20-year projections are likely overestimating net wealth by as much as 25%.…