Back dating a use of home as office expense and the implications

If the directors of the business submitted an expense form for the 'use of home' as an office what would the tax implications be to them personally assuming the cliam was fair, reasonable and justifiable?

This claim has never been made in the company's 5 year existance. They would like to backdate this claim for the last 5 years. What would the tax implications (if any) be of this?

Thanks