Within Service Manager invoices are created in batches, we call these 'Invoice Runs'. We take all of the customers who are due an invoice for a date range and batch them together ready to be emailed or printed.
Every customer has an agreement and on every agreement there are fields affecting how and when the invoice is created.
The 'Next Invoice Date' shows when the invoice is due to be created for the customer, in the case it's on '01/04/2021'.
When you create an 'Invoice Run' you'll most likely ask for all invoices that are due to be created for April 2021. As this agreement has a next invoice date of '01/04/2021' it will be included in that batch. See How to: Create an Invoice Run. The 'Next Invoice Date' is also the Invoice Date that appears at the top of your invoice report.
'Service From' and 'Service To' denotes what period your are charging for. In this example we are charging for the period '01/04/21' to 30/04/21' this means you are charging for the services provided in advance. See How to: Invoice In Advance or Arrears
If the customer had a Mat costing £120 per annum and wanted to be invoiced monthly it would show the following line on the invoice.