Accountancy (profession) or accounting (methodology) is the measurement, disclosure or provision of assurance about financial information that helps managers, investors, tax authorities and other decision makers make resource allocation decisions. Financial accounting is one branch of accounting and historically has involved processes by which financial information about a business is recorded, classified, summarized, interpreted, and communicated.

Auditing, a related but separate discipline, has two sub-disciplines: Internal and External auditing. External auditing is the process whereby an independent auditor examines an organization's financial statements and accounting records in order to express an opinion — that conveys reasonable but not absolute assurance — as to the truth and fairness of the statements and the accountant's adherence to Generally Accepted Accounting Principles (GAAP), in all material respects.

Internal auditing is an examination in which management, and not the external public, is the main beneficiary. It is carried out usually by auditors employed by the company, but sometimes by external service providers. The internal auditor's role is broader, and basically depends on what kind of assurance management wants. It usually certifies the efficiency and effectiveness of processes, departments, projects or internal controls. The Institute of Internal Auditors is generally accepted as the custodian of Internal Auditing best practice.

At the heart of accounting is the measurement of financial transactions which are transfers of legal property rights made under contractual relationships. Non-financial transactions are specifically excluded due to conservatism and materiality principles.

Practitioners of accountancy are known as accountants. There are many professional bodies for accountants throughout the world. Many allow their members to use titles indicating their membership. Examples are Chartered Certified Accountant (ACCA or FCCA), Chartered Accountant (FCA, CA or ACA) and Certified Public Accountant (CPA).

Accountancy attempts to create accurate financial reports that are useful to managers, regulators, and other stakeholders such as shareholders, creditors, or owners. The day-to-day record-keeping involved in this process is known as bookkeeping.

At the heart of modern financial accounting is the double-entry bookkeeping system. This system involves making at least two entries for every transaction: a debit in one account, and a corresponding credit in another account. The sum of all debits should always equal the sum..