Jack Lange served in the AIF 1942-45, and was employed as a bank officer, Commonwealth Bank 1941-51. He was solicitor and key legal adviser to many of the credit union pioneers in 1960s, 1970s. Participated in team responsible for the 1974 23G tax exemption for credit unions. Hon. solicitor for NSW League in 1962 and legal adviser for AFCUL when it started in 1966.
He contributed to creation of the NSW Credit Union Act, also worked with CUFA from 1971 and assisted NSW Savings Protection Fund during 1970s, Hon. solicitor with the Australian Credit Union Historical Cooperative. He was awarded the Australian Credit Union Distinguished Service Award in 2000.
Jack Lange provided an oral history interview for the credit union movement in 1989 when he was interviewed by Richard Raxworthy.