Would there be income tax for site expenses?

Hello to everyone,

My father is working on the site as a site incharge. The company which has appointed him on the site always transfer lacks of rupees to his personnal account for the site work. Now we are confused that will it attract tax liability for the amount transfered by the company for site work? (He gets his salary also on the same account) If yes, then what step we should take in future so that we should not become liable for tax for companies own work.

Thank you