How to create proforma invoice for AP supplier?

Hello,

Please help us with how we can achieve the process of Proforma Invoice for the below mentioned business situations:

Suppliers provide a proforma invoice with VAT added in invoice first then the business makes an advance payment against the proforma invoice. Unless the supplier gets the payment against the proforma invoice, the VAT invoice is not issued to the business.
Proforma invoices are provided by suppliers to run advance payments to protect their cash outflow. When the supplier raises a proforma invoice to the UK company, their liability to HMRC starts at that point. In the next run, they must pay that VAT amount to HMRC.