iterest liability - Goods and Services Tax - GST

One of my clients is a government contractor who completed road construction work for the central government in 2018-2019. The central government paid the basic amount but not GST because officials told the applicant that no budget was allotted for GST. The applicant paid GST in 2022-2023 from yourself and then approached the high court. After the high court order, the department paid the GST amount. The question now is whether the applicant is liable for interest or not because the PWD did not paid GST to the applicant