Basil Mramba (75) and Daniel Yona (74) both from the ruling Chama Cha Mapinduzi party, were in government when they issued the tax exemptions between 2002 and 2004.
A Tanzanian court has sentenced former Finance Minister, Basil Mramba and former Energy and Minerals Minister, Daniel Yona to three years in jail over corruption charges.
According to documents seen by Reuters news agency, it was related to issuing illegal tax exemptions and "arbitrarily" awarding a contract to audit gold.
They are the highest-profile convictions in the government's anti-graft drive.
Lawyers said the ex-ministers would appeal.
Mramba Yona were accused of abusing their authority in 2002 when they were in government for the ruling CCM party.
The tax exemptions cost the government millions of dollars in lost revenues.