On account versus against a bill
Posting on account is fine for quick categorisation, and it is often the right answer for an advance or an unidentified receipt. It is the wrong answer when you need your ageing report to close out specific invoices.
When to open the transaction
Open it at ledger level when you need to:- allocate bill by bill,
- split one entry across several ledgers, for example a payment with bank charges or TDS,
- assign cost centres line by line, or
- check the bill reconciliation the AI has already done.