How Our Calculators Work
Every tool on NewTaxTools is built from the actual law, IRS publications, or Department of Education rules. Nothing is estimated or approximated without disclosure. This page shows what each calculator uses and how we arrive at the numbers.
Our approach
We read the primary source first: the statute text, the IRS form instructions, or the federal register notice. We build the calculator logic to match the formula in the source. We test against worked examples in official publications where available. When the law is ambiguous or guidance is pending, we note it in the disclaimer on that page.
Every calculator runs entirely in your browser. Your numbers are never sent to a server. The JavaScript source code is visible in your browser's developer tools if you want to verify the formulas yourself.
Tax deduction calculators
| Element | Source |
|---|
| $25,000 deduction cap | One Big Beautiful Bill Act, Sec. 101, amending IRC §224(b) |
| Income phase-out: $150,000 single / $300,000 MFJ | IRC §224(c) as added by OBBBA |
| Qualifying occupations | IRS Notice 2025-XX, Treasury tipped occupation list |
| Schedule 1-A, Part II | IRS Form Schedule 1-A instructions (2025) |
| Self-employment net profit cap | IRC §224(d)(2), net earnings from self-employment |
| Element | Source |
|---|
| Premium-only deduction (0.5x of 1.5x rate) | OBBBA Sec. 102, amending IRC §225(a) |
| $12,500 cap single / $25,000 MFJ | IRC §225(b) |
| FLSA-required overtime only | IRC §225(c), referencing FLSA §207(a) |
| Income phase-out: $150,000 / $300,000 | IRC §225(d) |
| W-2 Box 12 Code TT | IRS Form W-2 instructions (2026) |
| Element | Source |
|---|
| $10,000 interest cap | OBBBA Sec. 103, amending IRC §226(b) |
| US final assembly requirement | IRC §226(c)(2), referencing 49 USC §32304 |
| VIN lookup API | NHTSA vPIC API (vpic.nhtsa.dot.gov), Plant information field |
| Income phase-out: $100,000 / $200,000 | IRC §226(d) |
| Form 1098-VLI | IRS Notice 2025-XX, new information reporting requirement |
| Element | Source |
|---|
| $6,000 per person age 65+ | OBBBA Sec. 104, amending IRC §227(a) |
| Phase-out: $75,000 single / $150,000 MFJ | IRC §227(b), 6% reduction rate |
| Complete phase-out: $175,000 / $250,000 | IRC §227(b)(2) |
| Age 65 requirement | IRC §227(c), age determination by end of tax year |
| Element | Source |
|---|
| $40,000 base cap (2025), $40,400 (2026) | OBBBA Sec. 201, amending IRC §164(b)(6) |
| 1% annual increase through 2029 | IRC §164(b)(6)(B) |
| Phase-down above $500,000 ($505,000 for 2026) | IRC §164(b)(6)(C), 30% reduction rate |
| Reversion to $10,000 after 2029 | IRC §164(b)(6)(D), sunset provision |
Student loan calculators
| Element | Source |
|---|
| 1%–10% of AGI graduated brackets | OBBBA Title IV, Sec. 401, Repayment Assistance Plan provisions |
| $50/month dependent credit | RAP program regulations, 34 CFR Part 685 |
| $10 minimum payment | Department of Education RAP program guidance |
| Unpaid interest waiver | RAP program regulations, interest subsidy provision |
| $50/month minimum principal reduction | RAP program regulations, principal guarantee |
| 30-year forgiveness | OBBBA Sec. 401, forgiveness timeline |
| Element | Source |
|---|
| 10% (new) or 15% (old) of discretionary income | 20 USC §1098e, Income-Based Repayment |
| 150% of poverty line threshold | 20 USC §1098e(a)(3)(B) |
| 2026 poverty guidelines | HHS Federal Poverty Guidelines, 91 FR (2026) |
| Standard plan payment cap | 20 USC §1098e(a)(3)(A) |
| Element | Source |
|---|
| 120 qualifying payments | 20 USC §1087e(m), Public Service Loan Forgiveness |
| Tax-free forgiveness | IRC §108(f)(1) |
| Qualifying employer types | 34 CFR §685.219(b), PSLF regulations |
Reference rates and figures
| Figure | Value (2026) | Source |
|---|
| Standard deduction, single | $16,100 | IRS Rev. Proc. 2025-32 |
| Standard deduction, MFJ | $32,200 | IRS Rev. Proc. 2025-32 |
| Standard deduction, HOH | $24,150 | IRS Rev. Proc. 2025-32 |
| Additional senior deduction, single | $2,050 | IRS Rev. Proc. 2025-32 |
| Additional senior deduction, MFJ (per spouse) | $1,650 | IRS Rev. Proc. 2025-32 |
| Federal poverty line, 1 person | $15,650 | HHS 2026 Poverty Guidelines |
| Federal poverty line, each additional | +$5,500 | HHS 2026 Poverty Guidelines |
Editorial standards
NewTaxTools is built and maintained by a small team with backgrounds in finance, tax research, and software engineering. Every calculator is reviewed against the primary legal source before publication. When IRS guidance is pending or ambiguous, we note it explicitly in the page disclaimer rather than guessing.
We do not sell financial products, accept sponsored content, or receive compensation from loan servicers, tax software companies, or financial institutions. The site is supported by advertising only. Our recommendations are based solely on the math.
If you find an error in any calculator, email contact@newtaxtools.com with the specific issue and we will correct it within 24 hours.
Section references are to the One Big Beautiful Bill Act as enacted, the Internal Revenue Code as amended, and Title 20/34 of the US Code and Code of Federal Regulations. Some section numbers may be updated when the IRS publishes final regulations. This page is for transparency, not legal advice.