Accounting systems and ERPs

An ERP (enterprise resource planning system) is a set of integrated modules — sales, purchasing, inventory, fixed assets, cash management and the general ledger — sharing one database of master data: customers, suppliers, items, employees and the chart of accounts. Products range from large enterprise suites to mid-market cloud systems and small-business accounting packages, but the architecture is the same.

Sub-ledgers and the general ledger. Each operational module keeps its own detailed ledger. The accounts receivable sub-ledger knows every open invoice for every customer; the general ledger holds a single control account, Accounts receivable, whose balance should equal the sum of that detail. The same applies to payables, inventory and the fixed asset register. The GL is where financial statements come from; the sub-ledgers are where the detail lives.

Posting rules (often called account determination) decide which GL accounts a business event hits. When a warehouse clerk ships an order, nobody types a journal: the system knows that a goods issue for a stock item debits cost of sales and credits inventory at the item's cost, because configuration maps item groups to accounts. That's why ERP accounting is mostly configuration and master data quality — a wrong mapping posts every transaction wrongly, silently and consistently.

Not every step posts. A sales order or purchase order is a commitment, not a transaction: it creates no entry. Postings happen at the economic events — goods shipped or received, invoice issued or received, cash paid or received.

Control accounts are usually blocked for manual journals. If someone could post directly to the AR control account, the GL would no longer equal the sub-ledger, and nobody could say which customer the amount belongs to. Corrections go through the sub-ledger (a credit note, a reversal) so detail and total move together.

Interfaces. Many businesses run payroll, point-of-sale or e-commerce platforms outside the ERP and send summary journals across an interface. Each interface needs a control: record counts and totals in the source report agreed to what was posted, with failures alerted rather than silently skipped.