You might receive a letter about an odd amount on a return asking for documentation. A strange claim of millions would likely earn a human audit which would uncover the truth. Keep in mind you can be found guilty for intentionally false tax returns of any kind.

A small discrepancy like forgetting to note wastage would never be caught, assuming it didn’t make it to Quickbooks initially. There has to be some ability to detect and audit what happened in order to correct it. This is partly why restaurants have been historically useful for laundering and fronting criminal operations.