You can find all your invoices in the Plan and billing section of your GetProspect account and download them from there.
Click the settings icon in the right upper corner of your account, then go to the Plan and billing. Navigate to Billing history tab. There you will find all your payments and you can download the invoices in PDF format.
By the way, in the Billing tab you can change the information for your invoices and input the email address where invoices will be sent after charges.