We receive funds from customers up to three months before we raise an invoice. how do I transfer these amounts from the bank account into the individual sales ledger?

Thanks for posting your question in the Intuit Community, michael32,

Let me get the help you need in recording advance invoice payment.

In QuickBooks Online, there are different ways on how to record Customer prepayments. With this being said, I'd recommend consulting your Accounting Professional. This is to ensure that VAT are recorded properly and on which method they've preferred.

To learn more on how to record Customer prepayments for Products or Services, you can check out this article: https://quickbooks.intuit.com/community/Manage-Customers-and-Income/How-to-record-Customer-prepayments-for-Products-or-Services/td-p/239560.

If you have further questions in recording payments, please feel free to reach back out. Have a great day!