To file your Schedule C you need to following records:
- Gross receipts from your trade or business.
- Business Expenses that show costs of operating your business.
- Expenses for business use of your home.
- Information on business use of your vehicle.
- Any other business related expenses you might have.
You need to collect these records for the full tax year, typically starting January 1st.
For more information see IRS site Business Taxes for the Self-Employed: The Basics