Is it haraam for me to add those hours in the invoice if there is no work?

Salaam, I have a question: I work in a Norwegian company as a software developer. they pay me on hour bases, I add my working hours in the final invoice and send it to them at the end of each month. sometimes the manager doesn't reply or give me daily tasks on time but I still have to be active on the chat application all day and reply to the chat questions to other team members if they ask. My question is. Is it haraam for me to add those hours in the invoice if there is no work? and I am just chatting or waiting for the manager to give me tasks? Please let me know.