Jersey now has a tax information exchange agreement with South Africa and the Czech Republic.
Senator Freddie Cohen, the assistant chief minister for international relations, was present at the signing of both agreements in London on Tuesday.
The agreements allow the exchange of information on request.
This is part of ongoing work to sign tax exchange agreements with all European Union and G20 countries.
Jersey has signed 23 tax information exchange agreements.
Jersey has sought to sign tax agreements with every one of the 19 G20 member jurisdictions, the 20th member being the European Union.
To date, 11 tax information exchange agreements have been signed with G20 members with six others close to being agreed.
Senator Cohen said: "The signing of a tax information exchange agreement with South Africa is of particular significance, not only because South Africa is a G20 member country but because business links between Jersey and South Africa are already strong and we believe they will be further strengthened by this agreement."