Enter your business name, address, and contact information in the top left corner of the form. 2. Enter information about your business’s formation, structure, and activities. 3. Indicate whether you are filing a Short Form or Long Form 1120. 4. Enter your taxable income, deductions, and credits. 5. Calculate your tax liability. 6. Enter your total payments and any balance due. 7. Sign and date the form. 8. Make sure to include all required schedules and supporting documents.