1Upload your documents
Drop everything here — paystubs, W-2s, 1099-NECs, in-year earnings statements (Uber, Lyft, etc.), and last year's 1040 & CA 540. Read locally; nothing is uploaded. We sort each file: paystubs/W-2s → income sources, 1099s & gig statements → self-employment income (they add up across the year), returns → the prior-year fields in Step 2.
Income sources (paystubs / W-2s)
Self-employment / 1099 income (independent contractor)
Optional — leave empty if none. Add a card per payer (Uber, DoorDash, a client, etc.). 1099 income has no withholding, so it usually means estimated payments. We total your net profit, self-employment (SE) tax, and roll both into the federal & California estimate below.
Net profit = gross + tips − expenses − mileage (miles × the 2026 standard rate), summed across payers. SE tax = 15.3% on 92.35% of net profit (12.4% Social Security up to the wage base + 2.9% Medicare); half is deducted from income. The W-2 field only matters if the same person with the 1099 also has a W-2 — it lowers the Social Security portion. California has no separate SE tax, but the net profit is still California taxable income.
Social Security benefits & FICA
Optional — leave at 0 if none. Enter Social Security benefits you receive (retirement, SSDI, or survivor — box 5 of the SSA-1099). Up to 85% is taxable federally depending on your other income; California does not tax Social Security at all, so the tool removes it from your California income automatically.
How much of your benefit is taxed depends on your provisional income = your other income + tax-exempt interest + half your benefits. Below $32,000 (married joint) / $25,000 (single) none is taxed; above $44,000 / $34,000 up to 85% is. We compute the exact taxable slice from all the other income you entered.
FICA already withheld from wages (Social Security & Medicare)
From your paystub/W-2 (boxes 4 & 6). This is a separate tax from income tax — it does not reduce the income tax estimated below. We track it to flag excess Social Security tax: if two or more employers each withheld up to the annual cap, the overage is a refundable credit on your federal return.
Investment income (interest, dividends, capital gains)
Optional — from your brokerage 1099-INT / 1099-DIV / 1099-B. Long-term capital gains and qualified dividends get the federal 0% / 15% / 20% preferential rates (stacked on top of your other income); short-term gains, ordinary dividends, and interest are taxed at your regular rates. California taxes all of it as ordinary income (no preferential rate), and all of it counts toward the 3.8% Net Investment Income Tax.
Qualified dividends are a subset of your ordinary dividends (box 1b β€ box 1a) — enter the total in 1a and the qualified portion in 1b; don't add them twice. A net capital loss offsets up to $3,000 ($1,500 MFS) of other income; the rest carries forward. Special-rate gains (real-estate Β§1250 recapture 25%, collectibles 28%, QSBS) aren't modeled.
Passive rental income (Schedule E)
Optional. One card per property. Net rental income = rents − operating expenses − depreciation. Rental income is not subject to self-employment tax, but it is ordinary income for federal & California, and (with other investment income) may trigger the 3.8% Net Investment Income Tax. A net loss is generally passive: up to $25,000 can offset other income if you actively participate (phasing out between $100k–$150k of income); the rest is suspended and carries forward. Mark a property as Mexico to also estimate Mexican rental tax.
Schedule K-1 income (partnership / S-corp / trust)
Optional. One card per K-1. Enter the boxes that have amounts. Ordinary business income and guaranteed payments add to your income; tick "subject to SE tax" only if you're a general partner materially participating (limited partners and S-corp shareholders are usually not). Interest, dividends, and rental add to income and count toward the 3.8% investment-income tax. Net capital gain (box 9a) is treated as long-term — it gets the federal 0/15/20% preferential rate; qualified dividends (box 6b) too. California taxes all of it as ordinary.
Qualified Business Income deduction (Β§199A)
A federal deduction of up to 20% of qualified business income (your 1099/Schedule-C net profit + K-1 ordinary business income). It reduces federal taxable income only — California does not allow it. Overall cap: 20% of (taxable income β capital gains β qualified dividends).
Auto-fills to your 1099 net profit + K-1 ordinary income (override if different). Guaranteed payments, wages, interest, dividends, and capital gains are not QBI. Below the 2026 threshold ($201,750 single / $403,500 MFJ) you get the full 20%. Above it, an SSTB phases out to $0, and a non-SSTB may be limited by W-2 wages / property β that wage limit isn't modeled, so above-threshold non-SSTB figures are an optimistic upper bound.
2Prior tax return information
A few facts the paystub can't tell us. Last year's numbers come from your prior return (Form 1040 / CA 540).
Federal is calculated for everyone. Pick your state for a state estimate β all 50 states + DC are included (2026 or latest-published figures); no-income-tax states show a federal-only result. State figures are approximate (local/city taxes and some state-specific deductions/credits aren't modeled) β verify against your state's tax agency.
Leave last year's numbers at 0 if you don't have them yet — the tool will just use the 90% of this year safe harbor. Fill them in to unlock the usually-cheaper 100% / 110% of last year option.
A prior-year NOL carryforward reduces this year's taxable income, but post-2017 NOLs offset at most 80% of taxable income (Β§172) β the rest carries forward again. Applied to federal and California (they can differ; enter the controlling amount). California suspends the NOL deduction for 2024β2026 when income is $1M+.
Estimated payments already made this year (optional)
Quarterly 1040-ES (federal) and 540-ES (California) payments you've already sent. These add to what you've paid in, lowering the balance due and what's left to pay.
| Quarter | Federal (1040-ES) | California (540-ES) |
|---|---|---|
| Q1 β Apr 15 | ||
| Q2 β Jun 15 | ||
| Q3 β Sep 15 | ||
| Q4 β Jan 15 |
Projected full year
| Source | Wages | Federal tax withheld | CA tax withheld |
|---|---|---|---|
| Total (full-year projected) |
2026 tax brackets — your marginal-rate math
First we work down from your income to AGI and then taxable income; then tax is progressive — each slice of taxable income is taxed at its own 2026 rate, not your whole income at the top rate. The full IRS and state rate schedules are shown below (brackets your income doesn't reach are greyed out); long-term capital gains & qualified dividends get the federal 0/15/20% rates layered on top. Here's how the projected tax on the cards above is built up.
Federal (IRS)
California (FTB)
Bottom line: refund or adjust
If you pay estimated taxes instead: when & how much
Show the math
Every number above, step by step, so it can be checked.
Federal worksheet
California worksheet
Never miss a quarterly payment — free reminders
Get a heads-up before each estimated-tax due date so a deadline never sneaks up on you. Rather hand it off? Ask a CPA to review or file for you.
Free. We save the email (and phone, if you add it) only to send the reminders & updates you check above — sent from info@fastinsights.io, never sold or shared, opt out anytime. Standard text rates may apply.
Assumptions & tax constants
Editable so you can keep them current or match an exact return. Sources noted; verify before relying on them.
2026 federal & California figures used
| Standard deduction (2026) | Federal | California |
|---|---|---|
| Single / MFS | ||
| Married filing jointly | ||
| Head of household |
Federal brackets & standard deductions: IRS Rev. Proc. 2025-32 (2026 tax year). California: latest published FTB rate schedule & standard deduction (2025 tax year) used as a 2026 proxy — CA publishes official 2026 brackets later in the year; replace with exact figures when available. Safe-harbor rules: IRS §6654 and CA FTB Form 540-ES instructions.
🔒 Privacy: your tax figures are never uploaded or stored — the calculator runs in your
browser and clears when you close the page. The only data we save is the email/phone you give the reminders form (and
only if you opt in), used to send due-date reminders & updates from info@fastinsights.io — never sold or shared.
We may track anonymous, aggregate usage (clicks/visits), never personal or tax data.
State rates and brackets are sourced from each state's tax agency and are subject to change (states update them
through the year). Everything here is an estimate only and may not be correct — confirm against the IRS
and your state's tax site before you pay or file.
This tool produces an estimate only and is not tax or legal advice. It models long-term capital gains &
qualified dividends at the federal 0/15/20% rates and a simplified 20% Β§199A QBI deduction (federal only). Simplifications:
QBI W-2-wage/UBIA limits above the threshold aren't modeled (above-threshold non-SSTB figures are an optimistic upper bound);
special-rate gains (Β§1250 recapture 25%, collectibles 28%, QSBS) aren't covered; AMT, most credits, and itemized deductions
beyond the standard aren't modeled; an NOL carryforward you enter is applied (80% limit; CA suspension over $1M) and the
federal NOL also lowers AGI-based items (Social Security taxability, NIIT); suspended passive/capital losses are flagged but
not carried between years; Mexican rental
tax is shown separately with no U.S./state foreign-tax credit applied. State estimates use 2026
or latest-published figures and are approximate β local/city income taxes (NYC, OH/PA municipalities, etc.), state-specific
retirement/cap-gains rules, and some exemptions/credits aren't modeled. Verify all figures against the IRS, your state's tax
agency, a Mexican contador (for ISR/IVA), and your own return or advisor before acting.