Quarterly estimated tax calculator and safe harbor check

Calculate quarterly estimated tax payments for {taxpayer_name} for {tax_year}.

Inputs:
- Prior year tax liability: {prior_year_tax}
- Current year projected taxable income: {projected_taxable_income}
- Withholding and credits: {withholding_credits}
- Safe harbor rules applicable: {safe_harbor_rules}
- Payments already made: {payments_made}

Output:
1) Estimated tax computation by quarter with due dates (assume standard schedule unless provided).
2) Safe harbor analysis and whether additional payments are recommended.
3) Sensitivity to income changes (±{sensitivity_pct}%).
4) Documentation notes and assumptions.

Flag jurisdiction-specific uncertainties.