At-a-glance checklist

  • Sole proprietors: Form 1040 (individual return) + Schedule C; estimated tax payments using Form 1040-ES if you expect to owe federal tax.
  • Partnerships: Form 1065 and Schedule K-1s for partners; partners report K-1 income on their individual returns.
  • Corporations (C corp): Form 1120.
  • S corporations: Form 1120-S and Schedule K-1s for shareholders.
  • Employment taxes: Form SS-4 to apply for an EIN if hiring; Form 941 (quarterly payroll), Form 940 (FUTA), and state payroll filings as required.
  • Information returns: 1099-NEC for nonemployee compensation and other 1099s or 1099-K where applicable.

Why these forms matter

Filing the correct forms ensures federal compliance, establishes a record for deductions and credits, and prevents penalties. The IRS provides specific return types and filing instructions by entity; see IRS — Small Businesses & Self-Employed (https://www.irs.gov/businesses/small-businesses-self-employed) and Forms & Publications (https://www.irs.gov/forms-pubs).

Brief descriptions and practical notes

  • Form 1040 + Schedule C: Used by sole proprietors to report business income and expenses on their personal return. Keep receipts and contemporaneous records of mileage, home office use, and business supplies. See our guide on filing Schedule C for practical tips: Filing Schedule C for Sole Proprietors: Tips and Pitfalls.

  • Form 1065 and Schedule K-1: Partnerships file 1065 to report partnership activity; income flows through to partners via K-1. Partners use the K-1 to report their share on personal returns; timely issuance of K-1s is critical for partners’ filings. For help choosing forms by entity, see: Choosing the Correct Business Tax Form: Schedule C vs S-Corp vs Partnership.

  • Form 1120 / 1120-S: Corporations file these returns; S corporations pass income to shareholders via K-1. Corporate rules on compensation, distributions, and deductions differ from sole proprietors—ask a tax adviser if unsure.

  • Employment filings: If you have employees, obtain an EIN (Form SS-4) and report payroll tax deposits and returns (Forms 941/940). Follow IRS Publication 15 (Employer’s Tax Guide) for withholding and deposit rules (https://www.irs.gov/publications/p15).

  • Information returns (1099s, 1099-K): If you pay independent contractors, you generally issue Form 1099-NEC. If you receive payments through third-party processors, you may receive a 1099-K; keep records to reconcile what’s reported. The IRS page on information returns explains thresholds and filing dates (https://www.irs.gov/forms-pubs/about-form-1099).

  • Estimated tax: Individuals and many pass-through owners pay quarterly estimated tax via Form 1040-ES to avoid underpayment penalties. Deadlines typically fall in April, June, September, and January of the following year; confirm current-year dates with the IRS.

Filing deadlines & extensions (practical guidance)

  • Partnership returns and S-Corp returns are generally due March 15; C-Corp returns and individual returns including Schedule C are generally due April 15. Deadlines can shift when they fall on weekends or holidays; you can request extensions (Form 7004 for many business returns, or Form 4868 for individuals) to avoid late-filing penalties, though an extension to file is not an extension to pay taxes owed.

Common mistakes first-time filers make

  • Using the wrong entity’s return (e.g., filing Schedule C when a partnership return is required).
  • Missing information returns (1099/1099-K) or failing to issue required 1099s.
  • Poor recordkeeping that prevents substantiating deductions.
  • Ignoring payroll tax responsibilities after hiring the first employee.

Professional tips

  • Start bookkeeping from day one using accounting software that can generate profit/loss reports and track receipts.
  • Apply for an EIN early if you plan to hire or form a corporation/partnership (IRS Form SS-4 guidance: https://www.irs.gov/forms-pubs/about-form-ss-4).
  • Work with a CPA for your first return or when changing entity type; correct classification (Schedule C vs. partnership/Corp) can materially affect taxes.

Related resources on FinHelp

Sources & authority

Professional disclaimer: This article is educational and not personalized tax advice. For help tailored to your business, consult a qualified CPA or tax advisor.