I'm hoping someone can help with info abt fringe benefits, i've been googling but am so confused about it

My DF gets fringe benefits from work but it doesnt go on his paycheck each fortnight... Do i tell centrelink the gross amount on his paycheck, then plus his fringe benefits??? or do i just tell them his gross amount on paycheck which doesnt include the fringe benefits
We have declared $15,000 fringe benefits in our yearly estimates but just not sure if we need to tell them fortnightly

Thanks in adance