Rationing was introduced at different stages for various commodities on both a national and local scale. The following give details of the nationally rationed items.

Sugar - National rationing existed from 31 December 1917 to 29 November 1920.

Butter - National rationing existed from 14 July 1918 to 30 May 1920.

Margarine - National rationing existed from 14 July 1918 to 16 February 1919.

Lard - National rationing existed from 14 July to 16 December 1918.

Butcher's Meat (Uncooked) - National rationing existed under Meat Scheme from 7 April 1918 and under General Scheme from 14 July 1918 until 15 December 1919.

Bacon and Ham - National rationing existed under Meat Scheme from 7 April and General Scheme from 14 July until 28 July 1918.

Jam - National rationing existed from 2 November 1918 to 15 April 1919.

Tea - This was not rationed nationally but its distribution was controlled by national registration of customers based on 2oz. per head from 14 July to 2 December 1918.

If you are interested in reading more about rationing during the First World War click here for details of how to visit the Department of Printed Books.

Sources:
British food control by Sir William H. Beveridge. - London: Humphrey Milford, Oxford University Press, 1928. (Economic and Social History of the World War : British series)