Creating an invoice can be done manually or using invoice software. Steps include: 1. Choose a Template: Select or design a professional template. 2. Fill in Details: Enter the seller and buyer information, invoice number, and date. 3. List Items: Add a detailed list of goods or services, including quantities and prices. 4. Calculate Totals: Add any applicable taxes and calculate the total amount due. 5. Specify Payment Terms: Clearly state the payment due date and methods.