War Tax Stamps WW1

[Andrew Tott]

I am looking for some information regarding War Tax stamps used in the First World War.
I have just purchased a card sent from Canada by a soldier that was back home in Canada recovering from wounds to his brother who was training  in England with the Canadian forces.
The card has a one cent green stamp on the back with War Tax stamped on it, after looking on the internet I did not realize that these stamps were used and how many British Commonwealth countries used them.
Canada was the first in February 1915 but there was about 27 countries used them then when Portugal entered the war in March 1916 six more Portuguese colonies were added.
My question is does anyone know of any reference material or books regarding this subject, information on the internet is a bit limited unless I am looking in the wrong place I keep seeing Stanley Gibbons reference numbers by some of the stamps but what catalogue would they be in, as I am not a stamp collector this is all new but I think I would like to try and collect some of these stamps.
Many thanks for any help or information regarding this ( sorry if it is not really a subject for this forum ) but I have always had response in the past from members of this forum.
Once again many thanks.
Andy

[Frank Schofield]

The only book I know on War Tax Stamps is:-

War Tax Stamps of The British Empire / West Indies by J.G.M Davis
Published by the Royal Philatelic Society in 2009

Frank Schofield

[Andrew Tott]

Many thanks for the information, have found the book on the internet but quite a bit of money for something that I am only thinking of collecting.
will try to find out more information on the net.
many thanks
Andy

[Alan Baker]

British Colonies and Dominions are listed under the relevant territory in Stanley Gibbons British Commonwealth (Part I) and presumably any from foreign countries are in the SG catalogue covering that country.

John Davis' book is pretty monumental but expensive and it does only cover BWI. He hasn't got round to looking at the other territories which issued war tax stamps, e.g. Fiji

I know the Royal were selling off residual stock quite cheaply but imagine they are all gone now