Mainstream corporation tax
 

 

Under the imputation system introduced in 1973 corporation tax collected from companies was divided into two parts, advance corporation tax is deducted at the standard rate of income tax from dividends paid. Undistributed profits are taxed once those profits have been agreed with the Inland Revenue and the tax, collected at a different date and often at a different rate due to budget changes, is known as mainstream corporation tax.

Reference: The Penguin Business Dictionary , 3rd edt.