Quick Answer

How to change from C Corp to S Corp comes down to one IRS form, one California state form, and a handful of eligibility boxes you need to check before the March 15 deadline. File Form 2553 with the IRS, submit FTB Form 3560 to the California Franchise Tax Board, and your corporation stops paying entity-level federal income tax effective the first day of that tax year. For a California business owner clearing $200,000 in annual profit, this single election can redirect $39,000 or more per year from the IRS and FTB back into your business. Most owners who delay even one year lose that entire amount permanently because there is no retroactive fix for a missed election window.

This information is current as of May 3, 2026. Tax laws change frequently. Verify updates with the IRS or FTB if reading this later.

Why the C Corp Default Costs California Owners $39,000 a Year

Every corporation formed in the United States starts life as a C Corp unless the shareholders affirmatively elect otherwise. That default classification sounds harmless until you run the numbers at tax time. A C Corp pays federal income tax at a flat 21% rate on its profits under IRC Section 11. When the remaining after-tax profit gets distributed to shareholders as dividends, those shareholders pay a second layer of federal tax at qualified dividend rates of up to 20%, plus the 3.8% Net Investment Income Tax under IRC Section 1411. California stacks its own 8.84% corporate franchise tax on top. The result is a combined effective tax rate that routinely exceeds 45% for California C Corp owners.

An S Corp, by contrast, is a pass-through entity. It pays zero federal income tax at the entity level. Profits flow directly to the shareholder’s personal return, taxed once at individual rates. California imposes a reduced 1.5% franchise tax on S Corp net income instead of 8.84%. There is no dividend double-taxation layer. And S Corp owners qualify for the permanent Qualified Business Income deduction under IRC Section 199A, which knocks up to 20% off qualifying business income before the individual rate even applies.

Here is what the five-layer gap looks like at three profit levels for a California single-filer with no other income sources:

Annual Profit	C Corp Total Tax	S Corp Total Tax	Annual S Corp Advantage
$100,000	$39,600	$22,000	$17,600
$200,000	$83,200	$44,000	$39,200
$350,000	$152,700	$88,000	$64,700

Those numbers account for the five tax layers: federal entity tax, federal dividend double taxation, the California franchise tax rate differential, the QBI deduction available exclusively to S Corp shareholders, and the AB 150 Pass-Through Entity tax election that allows S Corp owners to bypass the $40,000 SALT deduction cap signed into law permanently under the One Big Beautiful Bill Act (OBBBA). If you want to see your own numbers, plug your business profit into this small business tax calculator and compare the results side by side.

Key Takeaway: The C Corp default is not a neutral starting point. It is a tax penalty that compounds every year you do not elect S Corp status.

How to Change from C Corp to S Corp: The Complete 8-Step Process

The actual mechanics of switching from a C Corp to an S Corp are straightforward, but each step carries a compliance requirement that can disqualify or delay your election if handled incorrectly. Many business owners approach this as a simple form-filing exercise and end up triggering penalties, missing deadlines, or creating audit exposure they did not anticipate. Here is the full process, step by step.

Step 1: Verify IRC 1361(b) Eligibility

Before you touch Form 2553, confirm your corporation meets every S Corp qualification test under IRC Section 1361(b). You must be a domestic corporation with no more than 100 shareholders. All shareholders must be U.S. citizens or resident aliens, or qualifying trusts and estates. You can have only one class of stock (though voting rights can differ). If you have a nonresident alien co-owner, a corporate shareholder, or a partnership interest holder on your cap table, you cannot elect S Corp status. Period.

Step 2: Evaluate Built-In Gains Tax Exposure

When a C Corp converts to an S Corp, any appreciated assets held at the time of conversion remain subject to the Built-In Gains (BIG) tax under IRC Section 1374 if sold within the five-year recognition period. The BIG tax rate is 21% at the federal level, applied on top of normal shareholder-level taxation. If your C Corp owns real estate, equipment, or intellectual property that has appreciated significantly, get a professional appraisal before filing. That appraisal establishes your fair market value baseline on the conversion date and prevents the IRS from assigning a higher built-in gain later.

Step 3: Clean Up Accumulated Earnings and Profits

C Corps generate Accumulated Earnings and Profits (AE&P) under IRC Section 312. When you convert to an S Corp, that AE&P does not disappear. It follows the corporation and creates a contamination risk under IRC Section 1368(c). If your S Corp has AE&P and generates passive investment income exceeding 25% of gross receipts for three consecutive years, the IRS can automatically terminate your S Corp election under IRC Section 1362(d)(3). The fix is to distribute all AE&P as a dividend before or immediately after the election takes effect. Your tax advisor should calculate the exact AE&P balance and structure a distribution that eliminates this poison pill.

Step 4: File IRS Form 2553 by March 15

Form 2553, Election by a Small Business Corporation, must be filed no later than two months and 15 days after the beginning of the tax year you want the election to take effect. For calendar-year corporations, that deadline is March 15. File it one day late and you wait an entire additional year for S Corp treatment, losing the full annual tax savings described above. For a deeper walkthrough of the S Corp election strategy, review our comprehensive S Corp tax guide for California. All shareholders must sign the consent section on Form 2553, or attach a separate signed consent statement. Mail the form to the IRS service center designated for your state or fax it to the number listed in the form instructions. Keep your fax confirmation or certified mail receipt as proof of timely filing.

Step 5: File California FTB Form 3560

California does not automatically honor your federal S Corp election. You must separately notify the Franchise Tax Board by filing Form 3560, S Corporation Election or Termination/Revocation. Many owners assume the IRS election carries over. It does not. Skipping Form 3560 means California continues taxing your corporation at the C Corp rate of 8.84% even though the IRS treats you as an S Corp. That is a $14,680 mistake on $200,000 of profit, every single year you fail to file.

Step 6: Establish Reasonable Salary and Payroll

Every S Corp shareholder who works in the business must receive a reasonable salary and run formal payroll. “Reasonable” is defined by the IRS nine-factor test from Revenue Ruling 59-221, upheld in Watson v. Commissioner (T.C. Memo 2012-167). Factors include training, experience, duties performed, time devoted, comparable salaries in similar businesses, and the corporation’s dividend history. If the IRS determines your salary is unreasonably low, it can reclassify distributions as wages, assess back payroll taxes, add late deposit penalties under IRC Section 6656, and stack accuracy-related penalties under IRC Section 6662 on top. Register with the California Employment Development Department (EDD), set up state withholding, SDI at 1.1%, and Employment Training Tax. Most owners at $200,000 profit find a salary between $85,000 and $110,000 defensible.

Step 7: Activate AB 150 Pass-Through Entity Tax Election

California’s AB 150 allows S Corps to make a Pass-Through Entity (PTE) tax election, paying a 9.3% entity-level tax that generates a dollar-for-dollar credit on each shareholder’s personal return. This effectively bypasses the $40,000 SALT deduction cap made permanent under OBBBA. The election must be made annually by the original due date of the S Corp return (March 15 for calendar-year filers, or the extended due date if filed on extension). Missing this election means your California state tax liability sits behind the SALT cap with no workaround, costing high-income owners thousands in lost federal deductions.

Step 8: Set Up Dual Federal and California Depreciation Schedules

California does not conform to federal bonus depreciation under IRC Section 168(k) per Revenue and Taxation Code Sections 17250 and 24356. That means your S Corp needs two separate depreciation schedules: one for federal (which allows 100% bonus depreciation on qualifying assets under OBBBA’s permanent extension) and one for California (which follows the standard Modified Accelerated Cost Recovery System without the bonus). Failing to maintain dual schedules creates year-end reporting errors on both your federal Form 1120-S and California Form 100S, which the FTB and IRS both flag during automated matching. Our entity formation services include full depreciation schedule setup to prevent exactly this kind of compliance gap.

Key Takeaway: The election itself is one form. The compliance ecosystem around it involves eight distinct steps, each with its own penalty for failure.

Five Costly Mistakes That Derail the C Corp to S Corp Conversion

Filing Form 2553 is the easy part. The mistakes that cost California owners real money happen in the details most people never think to check.

Mistake 1: Treating the March 15 Deadline as Flexible

The March 15 deadline is not a suggestion. It is a statutory cutoff. If your form arrives March 16, your election does not take effect until the following tax year. At $200,000 in profit, that one-day delay costs $39,200. There is late election relief available under Revenue Procedure 2013-30, but it requires you to demonstrate reasonable cause and is not guaranteed. Do not bank on it.

Mistake 2: Skipping the BIG Tax Appraisal

If your C Corp owns any asset that has appreciated in value, the five-year BIG tax window under IRC Section 1374 applies. Selling that asset without a conversion-date appraisal means the IRS can assign a higher built-in gain than what actually existed. A $250,000 building that appreciated $100,000 before conversion and another $80,000 after conversion should only trigger BIG tax on the $100,000. Without an appraisal, the IRS may assess BIG tax on the entire $180,000 gain. That is $37,800 in unnecessary tax at the 21% federal rate, before state taxes.

Mistake 3: Ignoring AE&P Contamination

Accumulated Earnings and Profits from your C Corp years do not evaporate when you elect S Corp status. If you fail to distribute AE&P and your S Corp later generates passive investment income exceeding 25% of gross receipts, the IRS imposes a corporate-level tax under IRC Section 1375 and can terminate your election entirely under IRC Section 1362(d)(3). This trap catches owners who hold investment accounts or rental properties inside their S Corp without realizing the passive income ratio is creeping toward the threshold.

Mistake 4: Setting an Unreasonable Salary

The IRS Palantir SNAP AI system cross-references Form 1120-S officer compensation against W-2 filings, 941 quarterly returns, and industry benchmarks. If your salary represents less than 30% of net profit with no documentation to support the number, expect a flag. The Watson v. Commissioner case established that simply paying yourself $24,000 on $200,000 of profit is indefensible. The court found that comparable work commanded $91,044 per year. Reclassification of distributions as wages triggers employer FICA, employee FICA, late deposit penalties, and accuracy penalties. The total exposure can exceed $28,000 on a single year’s return.

Mistake 5: Forgetting FTB Form 3560

California requires a separate state-level S Corp election via Form 3560. This is not a redundant form. Without it, the FTB taxes your corporation at 8.84% instead of 1.5%. On $200,000 of profit, that is an extra $14,680 per year in California franchise tax. Many owners discover this mistake only when they receive a California Notice of Proposed Assessment two years after filing, at which point they owe back taxes plus interest and penalties.

Pro Tip: File Form 2553 and FTB Form 3560 on the same day. Use certified mail with return receipt for both. Keep the receipts in your permanent corporate records file. This eliminates the most common compliance gap in the entire conversion process.

KDA Case Study: Sacramento Restaurant Group Owner Saves $41,800 in Year One

David ran a Sacramento-area restaurant group that had operated as a C Corp since 2019. His accountant at the time had set up the corporation without ever discussing entity election options. By 2025, David’s three locations were generating $230,000 in combined annual profit. He was paying $48,300 in combined federal and California corporate taxes, plus another $18,400 in dividend taxes when he distributed profits to himself. His total annual tax burden exceeded $66,700, an effective rate of 29% at the entity level before personal taxes even entered the picture.

When David came to KDA, we ran a five-layer tax comparison and identified $41,800 in immediate annual savings from converting to S Corp status. Here is what we did:

• Filed Form 2553 under Rev. Proc. 2013-30 late election relief (David had missed the March 15 deadline by two weeks)
• Filed FTB Form 3560 simultaneously to activate the California S Corp election
• Distributed $47,000 in accumulated AE&P as a one-time dividend to eliminate the passive income termination risk
• Set David’s reasonable salary at $98,000 based on Bureau of Labor Statistics data for restaurant general managers in the Sacramento MSA
• Activated the AB 150 PTE election to bypass the $40,000 SALT cap on his California tax
• Opened a Solo 401(k) with employer contributions of $23,000, reducing both federal and self-employment tax exposure
• Established dual federal and California depreciation schedules for $85,000 in kitchen equipment placed in service that year

David’s year-one savings totaled $41,800. His engagement fee was $5,800. That is a 7.2x return on investment in the first twelve months. Over five years, the projected savings reach $209,000 assuming stable profit levels. The AE&P distribution, Solo 401(k), and AB 150 election were all strategies David had never been offered by his previous accountant.

Ready to see how we can help you? Explore more success stories on our case studies page to discover proven strategies that have saved our clients thousands in taxes.

Three Narrow Scenarios Where Staying a C Corp Wins

Not every C Corp should convert. Knowing when to stay put is just as valuable as knowing how to change from C Corp to S Corp. Three specific situations justify keeping C Corp status.

Scenario 1: You Are Raising Venture Capital

Venture capital firms typically invest through preferred stock classes. S Corps are limited to one class of stock under IRC Section 1361(b)(1)(D). If your cap table requires preferred shares, convertible notes that convert to a different class, or corporate shareholders (like a VC fund structured as an LLC), S Corp eligibility is off the table. Forcing an S Corp election here would either violate the eligibility rules or require restructuring that kills the deal.

Scenario 2: You Qualify for QSBS Under Section 1202

Qualified Small Business Stock under IRC Section 1202 allows founders to exclude up to $10 million in capital gains (or 10x their cost basis, whichever is greater) when they sell C Corp stock held for at least five years. This exclusion applies only to C Corp stock. S Corp stock does not qualify. However, California does not conform to the federal QSBS exclusion under Revenue and Taxation Code Section 18152.5, meaning California taxes the full gain regardless. If you are planning a $5 million or greater exit and expect to relocate out of California before selling, the QSBS route could save more than an S Corp election would over the same period.

Scenario 3: Full Earnings Retention Below $250,000

If your C Corp retains all profits below the $250,000 accumulated earnings tax threshold under IRC Section 531, and you never distribute dividends, the double-taxation layer disappears. The flat 21% corporate rate can be lower than individual rates at high income levels. This scenario is narrow because most business owners need to pull money out of the corporation to live on, and the accumulated earnings tax penalizes corporations that hoard profits without a valid business purpose.

OBBBA Permanent Changes That Make 2026 the Best Year to Convert

The One Big Beautiful Bill Act signed into law made several previously temporary tax provisions permanent, creating a more favorable environment for S Corp conversions than any prior year:

• QBI Deduction (IRC 199A) is now permanent. S Corp shareholders get up to a 20% deduction on qualified business income with no expiration date. C Corp owners get none of this benefit.
• 100% bonus depreciation is permanent. S Corp owners can immediately expense qualifying asset purchases at the federal level (though California still does not conform under R&TC 17250/24356). C Corp owners also get bonus depreciation, but the S Corp pass-through structure combines it with QBI for a larger net benefit.
• Section 179 limit increased to $2.5 million. Both entity types benefit, but S Corp pass-through treatment creates a larger after-tax advantage.
• SALT cap is $40,000. The AB 150 PTE election allows S Corp owners to bypass this cap entirely. C Corp owners have no equivalent workaround.
• Estate tax exemption is $15 million. S Corp stock receives a stepped-up basis at death under current law, which can eliminate capital gains for heirs. C Corp stock also receives a step-up, but the double-taxation structure means less wealth transfers in the first place.

Key Takeaway: Every one of these permanent provisions tilts the math further toward S Corp status for California business owners earning between $75,000 and $500,000 in annual business profit.

What If You Already Missed the March 15 Deadline?

If the March 15 window has closed, you are not necessarily locked out for the full year. Revenue Procedure 2013-30 provides late election relief if you meet specific criteria. You must demonstrate reasonable cause for the late filing (common causes include reliance on a tax professional who failed to file, or a good-faith misunderstanding of the deadline). The election must be filed within 3 years and 75 days of the intended effective date. All shareholders must have reported income consistent with S Corp treatment since the intended effective date, meaning you cannot have already filed a C Corp return for the current year.

If Rev. Proc. 2013-30 does not apply, you can request a Private Letter Ruling from the IRS at a cost of approximately $15,300. This is the last resort and involves a lengthy review process with no guaranteed outcome. The smarter play is to file on time. Mark the deadline now and do not rely on your memory or your accountant’s reminder system alone.

IRS Palantir SNAP AI: What Gets Flagged After Conversion

The IRS deploys Palantir’s SNAP AI system to cross-reference S Corp filings against multiple data points. After a C Corp to S Corp conversion, the following patterns trigger automated review:

• Salary-to-distribution ratio below 30%. If your W-2 salary is $30,000 and your K-1 distributions total $170,000, expect a flag.
• Missing 941 filings. S Corp shareholders on payroll must have quarterly 941 filings. A gap in filings after conversion suggests the owner is taking distributions without salary.
• Sudden income drop on Form 1120-S. If your C Corp reported $200,000 and your first S Corp year reports $80,000, the system flags the discrepancy for potential income shifting.
• Form 7203 basis tracking gaps. Shareholders must file Form 7203 to track stock and debt basis. Failing to file creates a negative inference about distribution legitimacy.
• AE&P distribution patterns. Large distributions in the year of conversion without corresponding dividend reporting on Form 1099-DIV raise automated questions.

None of these flags mean you did anything wrong. They mean you need documentation to prove you did it right. Keep your salary benchmarking study, your AE&P calculation worksheet, your BIG tax appraisal, and your AB 150 election confirmation in a single conversion compliance file.

Should You Convert? A Decision Framework

Yes, convert from C Corp to S Corp if:

• Your annual business profit exceeds $60,000
• You have 100 or fewer shareholders, all U.S. individuals or qualifying trusts
• You only have one class of stock
• You are not planning a VC raise requiring preferred shares
• You do not have a QSBS exit strategy worth $5 million or more
• You need to distribute profits to live on (most owners)

No, stay a C Corp if:

• You are raising venture capital or plan to within 24 months
• You qualify for QSBS and plan to exit above $5 million
• You retain 100% of earnings below $250,000 with a valid business purpose
• You have nonresident alien shareholders or entity-level shareholders

Frequently Asked Questions

Can I convert from C Corp to S Corp mid-year?

No. The S Corp election under Form 2553 must be filed by March 15 for calendar-year corporations and takes effect on January 1 of that year. There is no mid-year conversion option. If you miss the deadline, the earliest effective date is January 1 of the following year, unless you qualify for late election relief under Rev. Proc. 2013-30.

Do I need a new EIN after converting?

No. Your corporation keeps the same Employer Identification Number. The entity does not change; only its tax classification changes. Update your payroll records, bank accounts, and state registrations to reflect S Corp status, but the EIN remains the same.

What happens to my C Corp net operating losses after conversion?

C Corp net operating losses (NOLs) are suspended under IRC Section 1371(b) when you elect S Corp status. They do not carry forward to the S Corp return. However, they are preserved. If you ever revoke the S Corp election and return to C Corp status, the NOLs become available again. This is one reason to distribute AE&P and use any available NOLs before converting.

What is the five-year re-election lockout?

Under IRC Section 1362(g), if you revoke your S Corp election or it is terminated, you cannot re-elect S Corp status for five tax years without IRS consent. This lockout applies to voluntary revocations and involuntary terminations (such as the passive income termination trigger). Plan your conversion as a permanent structural decision, not a year-to-year tax play.

Does California automatically recognize my federal S Corp election?

No. You must file FTB Form 3560 separately with the California Franchise Tax Board. Without this filing, California taxes your corporation at the C Corp rate of 8.84% regardless of your federal S Corp status.

What is the minimum income level where conversion makes sense?

The payroll tax savings from S Corp status typically outweigh the additional compliance costs (payroll processing, 1120-S filing, reasonable salary documentation) when business profit exceeds approximately $60,000 to $75,000 annually. Below that threshold, the compliance costs can eat into or exceed the tax savings. Above $75,000, the math increasingly favors conversion in almost every scenario. Use IRS Publication 535 as a reference for deductible business expenses that affect your net profit calculation.

Book Your C Corp to S Corp Conversion Strategy Session

If you are running a California C Corp and suspect you are overpaying by thousands every year, you probably are. The five-layer tax gap does not shrink on its own, and every month you delay the conversion costs you real money. Book a personalized consultation with our strategy team. We will run your five-layer comparison, check your IRC 1361(b) eligibility, calculate your AE&P balance, and give you a clear, step-by-step conversion plan with projected savings for the next five years. Click here to book your consultation now.

“The IRS does not charge you extra for being a C Corp. It just never tells you there is a cheaper option sitting right next to it on the same form.”