Yeah that's a good question, you'll want to leverage the `overdraft` functionality for that, enabling the account end balance to go below zero.

So you could do something like:

    send [USD/2 10000] (
      source = @my_bank:loans_made allowing unbounded overdraft
      destination = @my_bank:1234
    )

With the post-transaction balance of @my_bank:loans_made becoming [USD/2 -10000]. So that's for creating money out of nothing.

There's a little bit more to it if you want to create accounting-perfect entries, but a simple way to map src/dest to cr/dr entries is to say that every credit becomes a destination, and every debit becomes a source.

You can then consider debit normal accounts as having their debit balance being equivalent to the sum of entries where the account is source, their credit balance as the sum of entries where the account is destination—and do the opposite for credit normal accounts.

We've written a bit more about it here [1].

[1] https://docs.formance.com/ledger/advanced/accounting/credit-...