The best definition of an accounting system is:

The concepts, principles, and standards specifying the information which should be included in financial statements, and how that information should be presented.

The personnel, procedures, devices, and records used by an entity to develop accounting information and communicate this information to decision makers.

Journals, ledgers, and worksheets.

Manual or computer-based records used in developing information about an entity for use by managers and also persons outside the organization.