Given that you know to apply a specific tax rule, the logic is formalized for the US. The problem is knowing when a specific tax rule applies to a given tax situation. In general, the IRS has an opinion — and not matching their opinion can land you in an audit — but the nuts-and-bolts application is still an interpretation. The IRS is, in my experience, pretty flexible with their interpretation. While individual auditors can have their hands tied with respect to fines/fee-schedules, I've always found them easy to work with, and knowledgeable. The last time I was audited, I ended up starting with a $220 fine; however, the auditor requested I review the previous several years of returns (for the same class of error), and I ended up getting a substantial check.