This paper describes the utility of the electrochemical technique for the preparation of a circular planar ²⁰⁴Tl source required for the calibration of beta surface contamination monitors. The electrolytic cell, the experimental set up used and the process of deposition are described. The factors that influence the electrodeposition of ²⁰⁴Tl onto the circular copper substrate were investigated and a careful control has been exercised to ensure an optimum deposition of the ²⁰⁴Tl activity onto the substrate. The morphology of the deposited layer was examined by SEM, AFM and EDS analyses. Sources containing ~3.7MBq (~ 0.1mCi) ²⁰⁴Tl on a copper sheet of 20 mm diameter working area were prepared and housed in a holder. Quality control tests on the leachability, distribution of activity and stability of the source were performed to ensure compliance with regulatory safety requirements.