Writing an invoice for hours worked, or a specific service rendered to another business or individual, requires a slightly different approach than that used for selling a tangible product. Rather than collecting an established retail or wholesale price, you are billing either for hours worked at an agreed upon rate, or a specific service performed for an agreed upon price. Invoicing for services rendered requires attention to detail.
Communicate to your clients when and how you are going to invoice them for your work. If you invoice a portion upfront before beginning a project, you need to inform your clients. If you bill work in progress rather than waiting until the completion of the contract, make sure that your client is in agreement. Many small businesses invoice electronically. Let your clients know that they will be receiving emailed invoices just so they don't accidentally delete them.
Keep good records. Compile the records of dates and hours worked and the nature of the services rendered. Review your project agreement or service contract to refresh your memory about the specific terms. Verify the name and address. Include the client billing reference number, if there is one. Include your own file reference number, if applicable.
Use a simple format. This makes the invoicing process more efficient. You can also use a software program to standardize your invoice format. Your invoice should include fields for invoice reference numbers, billing date, business name and address, and the name of the contracting officer to whom the invoice is being sent. Leave ample space to itemize the services rendered along with applicable project or product codes.
Specify the invoice amount. The hours may be the actual hours of service you provided at an agreed upon hourly rate, or the specific services you provided for the invoice amount. For example, if you are building a porch, you may have drawn up the plan, selected the lumber and laid the foundation for the frame during one billing period. You could list the activities and specify one lump-sum invoice amount. Or, you could list each activity separately, indicate the hours worked for each, and then calculate the invoice amount by multiplying the hours worked and the hourly rate.
Include supporting documents when appropriate. For example, if you had to use courier services or duplicating services to complete the tasks, attach copies of the receipts.