This introduction briefly describes the data on corporate income tax systems that has been collected by the Oxford University Centre for Business Taxation and is now available on this site. It provides a detailed information on all the variables available, the country and year coverage. Since the development of the database is an ongoing work, more information will become available over time. This note refers to the state of the database as of January 2017.

The information in this database for the years 2002 – 2012 has been used in the CBT Corporate Tax Ranking 2012. The database includes raw data variables such as corporate tax rates, aspects of the legal definition of the corporate tax base (depreciation rates and types), and inventory valuation methods. It also includes measures of EATRs and EMTRs as used in the CBT Corporate Tax Ranking 2012. The database covers G20 and OECD countries over the period 1983 – 2017 (in some case 1979 – 2017) as specified below.

The CBT database builds on an existing database which has been created in 2006 as a multi-country database and developed over the years by various Research Fellows at the Centre, and earlier at the Institute for Fiscal Studies. The original version uses various sources such as OECD Tax Database, IBFD (International Bureau of Fiscal Documentation), World Tax Database from the University of Michigan, KPMG and E&Y and covered mainly OECD countries. The data currently in the database comes from various sources, mainly from:

• The Worldwide Corporate Tax Guide published by E&Y; years available: 2002-2017
• Data for 2011 - 2017 comes mainly from the online IBFD Tax Research Platform where they provide very detailed Country Surveys
• G20 countries data has been updated to be consistent with IBFD "Global corporate tax handbook" (years 2007 - 2010) and "European tax handbook" (years 1990 - 2010)
• ZEW Intermediate Report 2011, “Effective Tax levels using Devereux/Griffith methodology”
• Deloitte Tax Highlights and International Tax and Business Guide; years available: 2009, 2010
• KPMG Tax Rate Survey; years available: 1998 - 2009
• PKF Worldwide Tax Guide; years available: 2007 - 2009

We update the database each year to make it consistent with the most recently available information. We aim to make sure that the all the information included in the database applies in 1 January of the given year. Therefore if the tax year is different than calendar year, any reforms introduced in a given tax year that started after 1 January will not appear in the data until the following year.

This brief description is organized as follows: section 2 lists all the countries covered in the sample, section 3 explains in more detail the features of each of the variables and what they comprise of. Section 4 explains how to obtain the data from the database and who to contact in case of any queries.