Long Service in the Tanzania Revenue Authority (TRA) since his recruitment in 1997 coupled with tremendous commitment to work exposed Robert T. Manyama to multiple career growth opportunities and experiences in customs and tax administration at large.

No sooner had Robert T. Manyama graduated Advanced Diploma in Tax Management (ADTM), at the Institute of Finance Management (IFM) in 1997 than was employed in the Customs Department on December the same year. He was enrolled for the Post Graduate Diploma in Tax Management (PGDTM) at the same Institute in 2003 and successfully graduated. That was five years after the first recruitment by TRA and was now a Senior Customs officer. The huge experience in customs operations and administration coupled with the practical field experiences imparted Mr. Robert T. Manyama with much knowledge in Customs and taxation; hence proficient in Customs laws and procedures besides tax administration.

In 2005 Robert T. Manyama joined Muenster University in Germany for a Master Degree in Customs Administration (MCA). MCA studies exposed him to International Trade rules, Treaties and multilateral agreements; Dispute Settlement processes besides the Alternative Dispute Resolutions (ADR) methods namely arbitration and Mediation processes. 

Robert T. Manyama ascended to Managerial posts in 2006 and became Assistant Manager Customs at the port of Dar es Salaam. Among his recorded successes included: successful operationalization of the Inland container Depots (ICD) for the first time in 2008 as cargo overflow storage facilities which significantly decongested the port of Dar es Salaam. The port had highly been crippled by severe cargo congestion between 2008 – 2012. Robert T. Manyama chaired a sub-committee of the Port Decongesting Committee which developed the Port Standard Operating Procedures (SOP). In 2012 to 2016 Robert was among members of the local Customs project team as in-charge of the Cargo Management Team which fully participated in the construction of the Cargo Management Modules currently incorporated in the Tanzania Customs Integrated System (TANCIS). Robert subsequently, became a Senior and permanent Instructor of the Customs studies at the Institute of Tax Administration (ITA).

In 2017 Robert T. Manyama was appointed Manager of the Customs Service Centre (CSC); then Manager Post Clearance Audit (MPCA) until 2021 when he became the Deputy Commissioner for Tax Investigation-operations, the post he held until March 2023. He was designated to post as Acting Tax Ombudsman under Secondment terms for one year. Robert was charged with the responsibility of establishing the Tax Ombudsman office and assure its successful operationalization by the end of November, 2023.