Marcus operates a business and was audited by the ATO. Throughout the audit he hindered the ATO by failing to attend scheduled meetings and failure to disclose important information. The auditor has discovered undisclosed income of $300,000 over four years, resulting in a tax shortfall of $100,000. The auditor is of the opinion that Marcus deliberately concealed the shortfall. The auditor also found that Marcus did not keep proper records of his transactions.

How much shortfall penalty is the ATO likely to charge?