Commercial cleaning services usually clients by the hour, the amount of which may fluctuate depending on the number of hours required to complete the job. The invoice will need to include a description of each service offered, the number of hours that the professional cleaner worked, the rate charged per hour ($/hr), the total amount due, and the date that the client is expected to pay by. If the service is provided on a routine basis, the service provider should send their invoices at regular intervals (weekly, bi-weekly, or monthly).