income tax, with an additional profits tax levied on companies. The Finance Act 1965 replaced this structure for companies and associations with a single corporate tax, which borrowed its basic structure and rules from the income tax system. Since 1997, the United Kingdom's Tax Law Rewrite Project has been modernising the United Kingdom's tax legislation, starting with income tax, while the legislation imposing corporation tax has itself been amended; the rules governing income tax and corporation tax have thus diverged. Business rates Business rates is the commonly used name of non-domestic rates, a rate or tax charged to occupiers of non-domestic property. Business rates form part of the funding for local government, and are collected by them, but rather than receipts being retained directly they are pooled centrally and then redistributed. In 2005–06, £19.9 billion was collected in business rates, representing 4.35 percent of the total United Kingdom tax income. Business rates are a property tax, where each non-domestic property is assessed with a rateable value, expressed in pounds. The rateable value broadly represents the annual rent the property could have been let for on a particular valuation date according to a set of assumptions. The actual bill payable is then calculated using a multiplier set by central government, and applying any reliefs. Business and personal taxes Some taxes are, depending on the circumstances, paid by both individuals and companies, and government National Insurance contributions The second largest source of government revenue is National Insurance contributions (NICs). NICs are payable by employees, employers and the self-employed and in the 2010–2011 tax year £96.5 billion was raised, 21.5 percent of the total collected by HMRC. Employees and employers pay contributions according to a complex classification based on employment type and income. Class 1 (employed persons) NIC is charged at several rates depending on various income thresholds and a number of other factors including age, the type of occupational pension scheme contributed to by the employee and/or employer and whether or not the employee is an ocean-going mariner. Certain married women who opted to pay reduced contributions (in return for reduced benefits) prior to 1977 retain this right for historical reasons. Employers also pay contributions on many benefits in kind provided to employees (such as company cars) and on tax liabilities met on behalf of employees via a "PAYE Settlement Agreement". There are separate arrangements for self-employed persons, who are normally liable