Data Source and Methodology
Authoritative data: Rhode Island Division of Taxation — Personal Income Tax Rate Schedule (RI‑1040 Instructions). See: Official RI Personal Income Tax (latest publication year) for rate thresholds and percentages. All calculations in this tool strictly follow the bracketed rate schedule published by the Rhode Island Division of Taxation. All computations are performed deterministically using those rates. All calculations are based rigorously on the formulas and data provided by this source.
The Formula Explained
Let taxable income be T, bracket thresholds be a₁ and a₂, and rates be r₁, r₂, r₃ (expressed as decimals).
Piecewise tax function:
TAX(T) = \begin{cases} r_1 \cdot T, & 0 \le T \le a_1 \\ r_1 \cdot a_1 + r_2 \cdot (T - a_1), & a_1 < T \le a_2 \\ r_1 \cdot a_1 + r_2 \cdot (a_2 - a_1) + r_3 \cdot (T - a_2), & T > a_2 \end{cases}
Effective rate:
\text{EffRate} = \dfrac{\text{TAX}(T)}{T} \quad (\text{defined as } 0 \text{ when } T=0)
Marginal rate:
\text{MargRate} = \begin{cases} r_1, & 0 \le T \le a_1 \\ r_2, & a_1 < T \le a_2 \\ r_3, & T > a_2 \end{cases}
Glossary of Variables
- Filing status
- Your filing classification (Single, MFJ, MFS, HOH). Rhode Island applies the same three brackets across statuses; however, deductions/exemptions (not modeled here) can vary.
- Rhode Island taxable income (T)
- Your income after RI adjustments, deductions, and exemptions, as used to compute state tax.
- Bracket thresholds (a₁, a₂)
- The upper ends of the first and second tax brackets. Income above a₂ is taxed at the top rate.
- Rates (r₁, r₂, r₃)
- Percentage rates for each bracket (e.g., 3.75%, 4.75%, 5.99%).
- State income tax (TAX)
- The total Rhode Island tax computed from the piecewise schedule.
- Effective tax rate
- Total tax divided by taxable income (TAX ÷ T).
- Marginal tax rate
- The rate that applies to your last dollar of taxable income.
- After‑tax income
- Taxable income minus state tax (T − TAX). This excludes other taxes/credits.
- Per‑period amounts
- Breakdowns by annual, monthly, biweekly, or weekly frequency for planning and payroll comparisons.
How It Works: A Step‑by‑Step Example
Suppose you file as Single with Rhode Island taxable income T = $120,000, and the default settings are: a₁ = $76,450, a₂ = $173,750, r₁ = 3.75%, r₂ = 4.75%, r₃ = 5.99%.
- Since a₁ < T ≤ a₂, use the second case of the piecewise function.
- Compute TAX(T) = r₁·a₁ + r₂·(T − a₁).
- r₁·a₁ = 0.0375 × 76,450 = $2,866.88 (rounded).
- r₂·(T − a₁) = 0.0475 × (120,000 − 76,450) = 0.0475 × 43,550 = $2,069.63 (rounded).
- Total TAX ≈ $2,866.88 + $2,069.63 = $4,936.51.
- Effective rate ≈ 4,936.51 ÷ 120,000 = 4.11%.
- Marginal rate = r₂ = 4.75% (because T is in the second bracket).
Note: Actual return values are rounded to the nearest cent; minor differences can occur due to rounding.
Frequently Asked Questions (FAQ)
Does the tool compute RI taxable income from my gross wages?
No. It requires your RI taxable income. Determining taxable income depends on adjustments, deductions, exemptions, and residency rules. Refer to the RI‑1040 instructions or consult a tax professional.
Do Rhode Island brackets change every year?
Thresholds are periodically adjusted. Use the “Customize brackets” panel to update the amounts to the latest official schedule if needed.
Is nonresident income supported?
Yes—enter RI taxable income (RI-source after apportionment). The rate schedule applies to taxable income regardless of residency, but your RI taxable amount may differ.
Are tax credits and phaseouts included?
This version does not model credits or phaseouts. Those are applied after the bracket computation on the return.
What about reciprocity or local payroll taxes?
Rhode Island has no local wage taxes in this model. Reciprocity and residency can affect what income is taxable in RI, but once taxable income is determined, the same bracket formula applies.
How precise are results?
The calculator uses exact arithmetic and rounds to the nearest cent for display. Always rely on the final filed return for authoritative amounts.
Last reviewed for accuracy on: .