Targets Using Separate Managerial and Tax Accounts

Hi,

Has anyone had experience with targets that maintain separate managerial and tax accounts? Specifically, I'm looking into a multi-unit medspa business where the seller has been underreporting revenue for tax purposes. The actual financials are kept in separate software, showing the true financial position of the business, although, I guess, this might not be auditable for QoE. Is this common? Should I continue the discussion (multiple is very low)? Are such companies fundable by investors in a self-funded acquisition (the SBA loan will not be necessary)? Aside from this issue, the business appears legit and appealing. Of course, post-acquisition, the company will immediately abandon this misleading reporting practice.