S corporations have federal filing requirements, shareholder reporting obligations, payroll responsibilities, and, in California, a separate state return. Missing one part of that calendar can create penalties and interest.
This article covers the 2024–2025 filing period. Its dates and amounts are historical and should be confirmed before being applied to another tax year.
Key federal dates
For a calendar-year S corporation filing its 2024 return, the principal dates included:
- January 31, 2025: W-2 forms were due to employees and the Social Security Administration.
- March 17, 2025: Form 1120-S was due because March 15 fell on a weekend.
- March 17, 2025: Schedule K-1 was due to each shareholder.
- March 17, 2025: Form 7004 was due to request an automatic six-month filing extension.
An extension to file does not automatically extend every payment obligation.
California Form 100S
An S corporation incorporated in California, doing business in California, or receiving California-source income may need to file Form 100S. California generally recognizes the federal S corporation election rather than requiring a separate state election.
California S corporations may owe the greater of the minimum franchise tax or a tax based on S corporation income. Current rates, exceptions, and first-year rules should be confirmed for the filing period.
Planning considerations
Maintain complete records
Keep income statements, balance sheets, expense support, payroll records, shareholder information, and prior-year returns together. Accurate books support the amounts reported on Form 1120-S, Form 100S, and Schedule K-1.
Review deductible expenses
Ordinary and necessary business expenses may reduce taxable business income when they are properly documented and allowed under current law. Personal and business costs should remain separate.
Evaluate California’s pass-through entity tax
Eligible entities may consider California’s elective pass-through entity tax. Eligibility, elections, payment dates, and the benefit to each shareholder require year-specific analysis.
Coordinate payroll and shareholder compensation
Shareholder-employees can have both payroll and ownership-related tax considerations. Compensation and distributions should be reviewed with a qualified professional rather than selected solely to reduce payroll tax.
Common mistakes
- Missing the Form 1120-S or Form 100S deadline.
- Providing Schedule K-1 late.
- Mixing personal and business expenses.
- Misclassifying workers.
- Failing to maintain support for deductions and credits.
- Treating an extension to file as an extension to pay.
- Allowing bookkeeping, payroll, and tax records to disagree.
Forms in brief
Form 1120-S reports an S corporation’s income, deductions, credits, and other federal tax information.
Schedule K-1 reports each shareholder’s share of relevant tax items.
Form 100S is California’s S Corporation Franchise or Income Tax Return.
Form 7004 requests an automatic extension of time to file certain business income-tax returns.
S corporation rules depend on the entity, shareholders, payroll, state activity, and tax year. Current advice should be based on the corporation’s complete records.