If you report 1,000,000 and certify that it's the right number, and the government audits you and find you should have paid 1,010,000, then depending on jurisdiction you might be entirely ok, or you might find you're not going to be paying just the difference, and interest, but also a fine, and bearing the cost of additional audits going forward, and that your finance director will not appreciate having to address questions aimed at figuring out whether anything criminal is involved. Repeat the mistake a few times, and the level of scrutiny will escalate.

There's a reason that in 28 years of working in software, the only thing the financial teams I've worked with have obsessed over have been whether or not we get the VAT calculations right, and the "sticker price" of the discrepancy has never been what they worry about. For calculations that does not involve getting tax amounts wrong, they often couldn't care less about much bigger discrepancies, but get tax wrong in the wrong jurisdiction and it's a lot of pain.

It's strange. In Russia, small error in VAT will get you a letter from tax service "pay us a small error voluntarily, or we will schedule an inspection". Letter will be automatically generated by ASK-NDS system (translated as Auto Check Vat).

How do they know there's an error?

Cross check with your contragents. For every bit of incoming VAT should be outgoing VAT from your supplier. And for outgoing VAT should be incoming VAT for your client and/or sale to physical customer.

If your incoming VAT are not matched with outgoing VAT from your supplier, you will be charged.

If your supplier declared VAT, but failed to pay it, you have choice: either you have to pay it or you will be inspected to proof that it was not a fake.

Every sale to physical customer in Russia should be uploaded to tax service cloud. You (as a customer) could check your receipt online or using app, and get a reward for reporting tax evasion.

This system boosted VAT revenue x1.5 in a few years.