Form 1120-S Explained: U.S. Income Tax Return for an S Corporation Guide for Small Business
What Form 1120-S is, who files it, when it's due, and how to fill it out. Complete guide for small business owners.
Form 1120-S is one of the forms every US small business eventually encounters. Here's everything you need to know.
What is Form 1120-S?
1120-S — U.S. Income Tax Return for an S Corporation
Purpose: S-Corp annual tax return
Filing deadline: March 15
Who must file Form 1120-S?
If you're a US-based business or self-employed individual, you likely need to file Form 1120-S if any of these apply:
- Your entity has elected S-Corp status via Form 2553
- Due March 15, two months earlier than C-Corps
How to complete Form 1120-S
The form can look intimidating, but the process breaks down into:
1. Collect the information (payee name, TIN, amount paid)
2. Fill out the form (paper or electronically)
3. Deliver copies (to recipient, IRS, and state if required)
4. Keep a copy for your records (7 years recommended)
Penalties for missing Form 1120-S
Penalties scale with how late you file:
- Up to 30 days late: $60 per form
- 31 days to August 1: $130 per form
- After August 1 or not at all: $330 per form
- Intentional disregard: $660+ per form
For a business with 10 unfiled forms, that's $6,600 in penalties — easily avoided by filing on time.
How TinSuite generates Form 1120-S
Instead of manually tracking, TinSuite auto-generates Form 1120-S at year-end:
- Contractor/employee data auto-populates from your records
- Amounts are pulled from payments/payroll data
- Generated PDF is IRS-ready
- Electronic filing supported