Invoices will be charged immediately after they are generated. If you have funds available in your Cloudways account, the invoice amount will be deducted from these funds. If there are not enough funds available to pay for the full invoice, the remaining amount will be charged from the registered credit card.
Depending on the infrastructure provider you use, you will receive invoices between the 1st and the 6th of every month. You can read more about invoicing here.