Hello,
I think I understand what you're trying to do. The good news is that this can all be done in QBO, the bad news is that it cannot be 100% automated. It WOULD require some actions by you every month.
1. You can setup recurring invoices to your clients every month and set them to automatically include any billable charges that have not been billed to your client yet.
2. You can also setup the template to create the invoice with a certain day on it but actually create the invoice days earlier. Ex: Invoice #100 is dated 4/10/2019 but its created in QBO on 4/7/2019.
Here are the parts that require a little work on your part.
1. You would have to either collect the billing info from your client and manually add it to their customer profile, OR you have to send the 1st online invoice to them and MAKE SURE they select the box when making a payment that says "Use this billing info for future payments".
2. With the recurring invoice template you can set the default invoice delivery to SEND LATER. This will create the invoice and put it in a queue. Then on whatever day you want to send your invoices, you just go to your invoice list and set filter to SEND LATER and then click batch actions and select SEND TRANSACTIONS. That will email all the invoices in the queue to the clients.
3. On the date you actually want to charge the customer, you would have to go to each open invoice for them and select receive payment. It will have their default billing method saved and then you just click OK and it will process the payment and close the invoice.
