Direct taxes provide only a small proportion of revenues, the greater proportion being derived from customs and excise duties and from foreign loans and grants-in-aid. Individuals are taxed on the basis of a graduated scale; companies are taxed at a flat rate on undistributed profits. The government revised the income tax system in March 1988 and enacted new sales taxes in April 1988 to broaden the tax base, improve tax collection, and rationalize the tax system.