From VoIP.ms Wiki
In order to get a VOIP.MS invoice, you can generate it yourself from the Finances Menu>> Generate Invoice in your Customer Portal.
Once you are there, you just have to specify a date range and click on the "Get invoice" button to generate your invoice.
You will get an invoice with your personal information and that displays all the charges (setup and monthly fees for your DIDs, CNAM queries, incoming and outgoing calls) and deposits for the range selected, similar to this:
At the bottom of the invoice, you will see a summary of the transactions, deposits and the ending balance.