THE BARATELLI INSTITUTE · Mentoring at Scale
FOR C-CORPS, S-CORPS, PARTNERSHIPS, AND LLCS — RUN IT YOURSELF, BRING IT TO YOUR CPA

The business-entity estimated-tax math your CPA is running. Run it before you pay the bill.

Federal Form 1120-W safe harbor analysis for C-corps, pass-through-entity tax (PTET) computation for S-corps and partnerships in the 33 states that have adopted it, quarterly schedule with due dates, and the SALT-cap workaround that most business owners and many CPAs are still missing — worth $20K-200K+/year in federal tax savings for many owners.

PTET
SALT-cap workaround
33+
States with PTET election
21%
C-corp federal rate
100%
Prior-year safe harbor (small corp)
YOUR ENTITY
1
Entity & basics
2
Income projection
3
Prior-year baseline
4
PTET decision
5
Quarterly schedule
STAGE 1 OF 5

Entity type & tax basics

Defaults model an S-corp with $500K projected ordinary income, single owner, in California — the textbook PTET-election candidate.

C-corp pays federal entity-level tax (21% flat) and files Form 1120-W estimates. S-corp / Partnership / LLC-as-pass-through generally don't owe federal entity-level tax (income flows to owners) — but the PTET state election creates an entity-level state tax that converts capped state SALT into uncapped federal deduction.
Calendar-year due dates: federal Q1 4/15, Q2 6/15, Q3 9/15, Q4 12/15 (C-corp) or 1/15 next year. Fiscal-year entities have different due dates — quarterly installments are due 4th, 6th, 9th, and 12th month of fiscal year.
Used for state estimated tax + PTET availability. PTET is currently elected in 33+ states; rates and mechanics vary materially. A few states (FL, TX, NV, WA, WY, SD, AK) have no individual income tax, so PTET is moot for residents of those states.
For S-corp/partnership: how many K-1 recipients? Drives owner-level analysis. For C-corp: ignored.
Why PTET matters more than most owners realize. Before TCJA capped SALT at $10K, business owners deducted state income tax on Schedule A. Post-TCJA, that deduction is largely lost for high-income owners. PTET is the workaround: the entity pays state income tax at the entity level, deducts it as a federal business expense (no $10K cap), and the owner gets a credit on their state return. For an owner with $500K of pass-through income in a 9% state, PTET is worth roughly $500K × 9% × 37% = $16,650/year of federal tax savings. Most CPAs still aren't electing it for every eligible client.
STAGE 2 OF 5

Current-year income projection

For C-corp: projected entity-level taxable income. For pass-through: projected ordinary income that flows to K-1s.

For C-corp: federal Form 1120 line 30 (taxable income). For pass-through: Form 1120S line 21 or Form 1065 line 22 — the ordinary business income that flows to K-1 box 1.
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For pass-through: items that flow to K-1 separately from ordinary income — interest, dividends, LTCG, §1231 gains, charitable contributions, §179 deductions. These flow to owners but aren't part of entity-level PTET base in most states.
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For pass-through PTET federal-savings calculation. Most pass-through owners with $500K+ of business income are at 32-37%. Used to compute the PTET federal deduction value (entity-paid PTET × owner's federal bracket = federal savings).
A corp with taxable income $1M+ in any of the 3 prior years is "large" — loses the 100% prior-year safe harbor and must pay 100% of current-year tax. (First-quarter exception: large corps can use 100% prior year for Q1 only, then must true up to current year for Q2-Q4.)
For pass-through: 20% of qualified business income at the owner's level. Phased out for SSTBs (specified service trade/business: law, health, accounting, consulting, financial services, etc.) above $483K MFJ / $241K single 2025. Auto-estimate 20% of pass-through income up to phaseout.
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Spouse W-2, other K-1s, investment income — anything flowing to the owner's 1040 outside of THIS business. Used to verify owner's marginal bracket assumption.
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STAGE 3 OF 5

Prior-year baseline (for safe harbor)

For C-corp small-corp safe harbor. For pass-through entities, this drives state PTET prepayment requirements (most states require 50%+ of prior-year PTET to be paid by mid-year).

For C-corp: prior-year Form 1120 line 31 (total tax). For pass-through: typically zero at federal entity level. Used for the small-corp 100%-prior-year safe harbor.
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For pass-through that elected PTET in prior year: total PTET paid (per K-1 footnote / state PTET return). Most states require 50%+ of prior-year PTET to be prepaid by mid-year of current year. CA: 50% of prior year by 6/15 (or $1,000 minimum if no prior year).
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Total of Q1 + Q2 + Q3 + Q4 federal entity estimates already paid this year. Reduces remaining quarterly need.
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Total state PTET prepayment already made this year. For CA: includes the mandatory June 15 prepayment (50% of prior year or $1,000).
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The CA PTET prepayment trap. California PTET requires a mandatory prepayment of the GREATER of $1,000 OR 50% of prior-year PTET by June 15 of the current year. Miss this prepayment and the entity LOSES the PTET election entirely for the year — you cannot make the election later. This is the most common PTET mistake. If you elected PTET last year and your CPA hasn't reminded you about the June 15 prepayment, ask. Other states have similar (but generally less punitive) prepayment rules.
STAGE 4 OF 5

PTET decision (pass-through entities only)

The single highest-leverage tax decision for many pass-through owners. Here is the math.

Most states require an annual election by a specific deadline (CA: by mid-year prepayment due date; NY: by 3/15 of current year; varies). For C-corp: PTET is N/A (income is taxed at entity level regardless).
PTET works best when owner is a resident of the same state where business operates (cleanest credit mechanic). If owner is a no-tax state resident (FL, TX, NV) earning K-1 income from a CA business, PTET still helps — converts non-deductible state-source income tax (which CA charges as nonresident tax) into federal deduction.
The PTET decision in one sentence. If your business is a pass-through, you operate in a PTET state, your owners have meaningful federal taxable income (so the federal deduction has value), and the state's PTET mechanics work cleanly with owner residency — elect it. Federal savings are typically 30-37% of state tax otherwise paid by owners on Schedule A (which is now capped at $10K). The downsides are mostly administrative: an extra return, the prepayment compliance, and the K-1 footnote disclosures. The math virtually always works for owners with $200K+ of state-source pass-through income.
STAGE 5 OF 5 · YOUR SCHEDULE

Your quarterly business estimated tax schedule

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Tax projection waterfall

Quarterly federal entity estimates

Quarterly state PTET schedule

Tax metrics

Recommendations

PAIRS WITH
Individual Quarterly Estimated Tax · CFO Engagement Profitability · CPA Firm Engagement
For owners with W-2 income or self-employment income outside this entity, the Individual Quarterly Estimated Tax tool covers personal estimates. The CPA Firm Engagement Profitability tool helps your CPA price the work fairly. Bring this output to your CPA review meeting — let them verify the PTET numbers and answer the entity-specific edge cases. Subscribe to the library →
CFO & FO REFERENCE GUIDES

Bring this to your CPA review. They'll thank you.

PTET election and prepayment compliance · entity quarterly schedule · safe-harbor analysis · QBI optimization at owner level · year-end conversion sequencing · the multi-year tax-rate-arbitrage planning that drives real after-tax wealth.

State PTET rates and mechanics vary materially by state and change frequently as legislatures refine the post-TCJA workaround. The model uses representative rates as of mid-2026 but does NOT separately compute: state-specific PTET base inclusions/exclusions (some states use only federal taxable income, others state taxable income), nonresident-owner credit availability, partnership vs. S-corp differences in PTET allocation, owner basis impact of PTET payments, federal AMT considerations, fiscal-year filing complications, or the "reverse PTET" interaction with state-residency planning. Engage a CPA familiar with multi-state PTET for your specific situation. This is not tax advice. The output should be reviewed by a qualified CPA before any payment or filing.
WANT THE METHODOLOGY BEHIND THIS TOOL?
This calculator is one chapter of CFO & Controller's Reference Guide.
The tool gives you the answer. The guide gives you the argument — the case law, the worked examples, the negotiation playbook, the cross-check tables, the exception cases. Read the chapter and you can defend your number to a board, a buyer, an examiner, or a counterparty.
The methodology behind this calculator is in Ch 30 Treasury & Banking of the reference guide.
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PROFESSIONAL DISCLAIMER · PLEASE READ

Educational and informational purposes only. This calculator and any output it produces are intended solely for general educational and decision-support purposes. They do not constitute investment, tax, legal, accounting, appraisal, lending, insurance, or any other professional advice, and they do not create a fiduciary, attorney-client, accountant-client, or advisor-client relationship of any kind.

Estimates based on your inputs. All results are estimates derived from the data and assumptions you provide. Tax law, accounting standards, regulations, market conditions, and the specific facts of your situation can materially change the answer. The Baratelli Institute, its affiliates, and any co-branding professional make no warranty of accuracy, completeness, currency, or fitness for any particular purpose, and disclaim all liability for decisions made in reliance on the output.

Consult your own qualified professionals. Before acting on anything calculated here, consult your own attorney, CPA, financial advisor, appraiser, lender, or other qualified professional licensed in your jurisdiction who has reviewed your specific facts and applicable current law. The Baratelli Institute is a publisher of practitioner reference material. It is not a registered investment adviser, broker-dealer, law firm, accounting firm, appraisal firm, or lender.

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