accounting in the United States concentrates on the preparation, analysis and presentation of tax payments and tax returns. The U.S. tax system requires the use of specialised accounting principles for tax purposes which can differ from the generally accepted accounting principles (GAAP) for financial reporting. U.S. tax law covers four basic forms of business ownership: sole proprietorship, partnership, corporation, and limited liability company. Corporate and personal income are taxed at different rates, both varying according to income levels and including varying marginal rates (taxed on each additional dollar of income) and average rates (set as a percentage of overall income). Forensic accounting Forensic accounting is a specialty practice area of accounting that describes engagements that result from actual or anticipated disputes or litigation. "Forensic" means "suitable for use in a court of law", and it is to that standard and potential outcome that forensic accountants generally have to work. Political campaign accounting Political campaign accounting deals with the development and implementation of financial systems and the accounting of financial transactions in compliance with laws governing political campaign operations. This branch of accounting was first formally introduced in the March 1976 issue of The Journal of Accountancy. Organizations Professional bodies Professional accounting bodies include the American Institute of Certified Public Accountants (AICPA) and the other 179 members of the International Federation of Accountants (IFAC), including Institute of Chartered Accountants of Scotland (ICAS), Institute of Chartered Accountants of Pakistan (ICAP), CPA Australia, Institute of Chartered Accountants of India, Association of Chartered Certified Accountants (ACCA) and Institute of Chartered Accountants in England and Wales (ICAEW). Some countries have a single professional accounting body and, in some other countries, professional bodies for subfields of the accounting professions also exist, for example the Chartered Institute of Management Accountants (CIMA) in the UK and Institute of management accountants in the United States. Many of these professional bodies offer education and training including qualification and administration for various accounting designations, such as certified public accountant (AICPA) and chartered accountant. Firms Depending on its size, a company may be legally required to have their financial statements audited by a qualified auditor, and audits are usually carried out by accounting firms. Accounting firms grew in the United States and Europe in the late nineteenth and early twentieth century, and through several mergers there were large international accounting firms by the mid-twentieth century. Further large mergers in the late twentieth