Form 1120-S Filing Guide for S-Corporations: 2026 Edition

S-Corporations file Form 1120-S annually — even though no entity-level federal income tax is owed (the income flows through to shareholders via Schedule K-1).

Filing deadline

March 15 of the year following the tax year (or the 15th day of the 3rd month after your fiscal year end). Six-month extension via Form 7004.

Late-filing penalty: $245 per shareholder per month (2025 amount, § 6699) for up to 12 months. A 5-shareholder S-Corp filing 3 months late = $3,675 penalty.

What you'll need

• Prior-year Form 1120-S and Schedule K-1s
• Year-end financial statements (Income Statement, Balance Sheet)
• Payroll records (W-2s, W-3, Forms 941)
• 1099-NEC forms issued and received
• Asset & depreciation schedule (Form 4562 carryover)
• AAA balance from prior year
• Shareholder ownership % records
• Health insurance premiums for >2% shareholders

The form, section by section

Page 1 — Income & Deductions

• Lines 1a-6: Gross receipts → COGS → Gross profit
• Lines 7-19: Standard deductions (officer comp, salaries, repairs, rents, taxes, depreciation, etc.)
• Line 20: Total deductions
• Line 21: Ordinary business income/loss

Schedule B — Other Information

• Accounting method (cash/accrual)
• Type of business
• Whether the corp is the parent of a controlled group

Schedule K — Shareholders' Pro-Rata Share Items Line items that flow to each shareholder's K-1:

• Line 1: Ordinary income (the pass-through)
• Line 2: Net rental real estate income
• Line 12a: Charitable contributions (capped at shareholder level)
• Line 16d: Distributions
• Line 17: Investment income/expense

Schedule K-1 (one per shareholder)

• Each shareholder's distributive share of every item on Schedule K
• Allocated by ownership % × days held
• Issued to shareholders with the 1120-S filing

Schedule L — Balance Sheet Required if total receipts ≥ $250,000 OR total assets ≥ $250,000

Schedule M-1 — Book → Tax Reconciliation Reconciles net income per books to ordinary income per return. The big differences:

• 50% meals disallowance (line 5)
• Tax-exempt interest (line 4)
• Federal tax (corps only)
• Depreciation differences

Schedule M-2 — AAA, OAA, Retained Earnings This is where most S-corps mess up.

Accumulated Adjustments Account (AAA):

• Beginning AAA (line 1) — pulls from prior year ending
• Ordinary income increases AAA (line 2)
• Distributions decrease AAA (line 5)
• Ending AAA = next year's beginning

If you converted from a C-Corp, you also have OAA (Other Adjustments Account) and AE&P (Accumulated Earnings & Profits from C-Corp years). Distributions follow ordering rules under § 1368:

1. From AAA → tax-free (return of basis up to basis)
2. From AE&P → taxable as dividends
3. From OAA → tax-free (return of basis)
4. Excess → capital gain

The 5 mistakes that get S-Corps audited

1. Zero officer compensation with high distributions — IRS routinely reclassifies as wages, assesses back FICA + 100% of penalties
2. Skipping the W-2 Box 1 add-back for >2% shareholder health insurance — Notice 2008-1 requires it
3. Distributions exceeding AAA + basis — improperly reported as tax-free when they should be capital gain
4. Not filing Form 7203 — required since 2021 to track shareholder basis (in addition to the K-1)
5. Mixing personal and business expenses — losing the corporate veil and inviting reclassification

Reasonable salary — the perpetual issue

Per Reg. § 1.162-7 and Rev. Rul. 74-44, shareholders providing services must take a "reasonable" W-2 salary before any distributions.

Common defenses:

• BLS Occupational Employment Statistics for your role + region
• Industry compensation surveys (RC Reports, RCReport)
• Job-duty analysis and time studies

A $30,000 salary on $300,000 of profit will get reclassified. A $90,000 salary with documented justification ("I work 25 hours/week, the rest is passive investment in my partnership") might survive.

How Accountaxed simplifies it

Accountaxed's tax engine generates a fully populated 1120-S with Schedule K, Schedule M-1, and Schedule M-2 AAA tracking when you upload your prior return. Compliance warnings flag:

• Reasonable-salary deficit (Wages < 20% of profit)
• Health insurance not added back
• AAA distributions exceeding available balance

Generate your 1120-S draft → · Form 1120-S Instructions