S Corp Compliance & Filing 2025
A comprehensive operational guide to maintaining "S" status: navigating Form 1120-S, Reasonable Compensation mandates, and Shareholder Basis traps.
Executive Summary
The S Corporation is a privilege, not a right. Maintaining this tax-advantaged status requires rigorous adherence to a compliance calendar that has become increasingly unforgiving. For the 2025 tax year, the IRS has lowered e-filing thresholds and increased penalties for late filings to $245 per shareholder, per month.
Beyond federal filings, operational leaders must defend against the two most common audit triggers: Reasonable Compensation (underpayment of FICA taxes) and Shareholder Basis (deducting losses in excess of investment).
The Deadline
The Mandate
The Form
2025 Compliance Calendar
Key Date: March 17, 2025
| Date | Form / Action | Notes |
|---|---|---|
| Jan 31 | W-2s & 1099s | Deadline to furnish to employees/contractors. |
| Mar 17 | Form 1120-S | Primary S Corp Return Due. |
| Mar 17 | Form 7004 | Automatic 6-Month Extension Request. |
| Sep 15 | Extended Return | Final deadline if Form 7004 was filed. |
The "Reasonable Compensation" Trap
The "Many Hats" Approach
Best for Small Ops: Break down your job into roles (Admin, Sales, CEO) and assign a market rate to each based on hours worked.
The "Independent Investor" Test
Best for High Profit: Would an independent investor be happy with their return (distributions) after paying your salary?
Shareholder Basis (Form 7203)
Basis is your "skin in the game." It determines if you can deduct losses and receive tax-free distributions.
The Ordering Rules (Crucial!)
Basis must be adjusted in a specific order every year. Getting this wrong causes tax penalties.
-
1
Increase for Income
Add profit (including tax-exempt income) to your starting basis.
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2
Decrease for Distributions
Subtract cash taken out. If distributions > basis, the excess is Capital Gain.
-
3
Decrease for Losses
Only after distributions do you deduct losses. If basis hits $0, losses are suspended.
State Compliance: Washington B&O
No Income Tax, but...
The Compensation Disconnect
Paying a high officer salary reduces Federal tax but does nothing for WA State tax.
Federal Profit: $100k (Taxed)
WA Taxable Base: $1M (Taxed)
Nexus Threshold
Even out-of-state S Corps owe B&O tax if they cross the economic nexus line.
- Threshold: $100,000 in WA-sourced gross receipts.
- Service Rates: ~1.5% - 1.75% of Gross.
Interactive: Reasonable Comp Estimator
Use the "Many Hats" Cost Approach to estimate a defensible salary. Break down your role by function and hours.
Functional Breakdown
Recommended Compensation
* This is a baseline estimate based on replacement cost. Actual reasonable comp may vary based on profitability and location.