How to link Contact information (main contact) to the Account module

How to link Contact information (main contact) to the Account module

Hello,

My company uses one field to flag a contact as a main contact, usually for price communication. I want to check if some accounts are missing a contact with ''main contact'' ticked. This would mean that we do not select them during corporate messages and this is an issue. 

If there an easy way to show the accounts without a main contact?

In a perfect world I'd also like to show all accounts with invoices but without main contact. 

Thank you!