In fact, the customer sells the prototype to you, and you process it and sell it to the customer.

Borrow when receiving processed products: goods entrusted for processing.

Taxes payable-VAT payable (input tax)

Loan: the payment for entrusted processing.

When processing cost occurs, borrow: production cost.

Loans: accounts payable/bank deposits, etc.

Borrowing when carrying forward costs: entrusted processing payment.

Credit: production cost

Borrowing when selling to the entrusting party: bank deposits/accounts receivable.

Loans: other business income

Taxes payable-VAT payable (output tax)

Borrowing when carrying forward: other business expenses

Payment for entrusted processed goods

Loan: entrusted processing goods.