Accountant here. It suprised me when I joined the field, but profit is calculated using a range of accounting estimates. Each accountant will make different decisions. Not least about which accounting period something belongs. Imagine a factory with freight inwards. It is month end and I have a sheaf of bills from various freight companies, but which ones are missing, not received yet? I can't wait, I have 2 days to report, so I make an estimate...now imagine that I have perhaps 100 such things. I may have to justify my estimates, but how should I estimate it? Same as last month? Perhaps I know there is a lot of shipments so I make it at the higher end.

Now I have a product failure at a major customer that I may have to send free replacements for. Should I recognise that cost now, or not? The accounting standards say if I know about it, and I can measure it and there is a high degree of certainty then I should. But the method of choosing is up to me. £10m or 1m cost, and this year or next... and I get to decide.

We bought a £6m dollar machine to be depreciated over time, but how long. The machine lasts 10 years, but will we still be using it then? Do I capitalise the internal R&D work as well?

All of which is audited, but the auditor often only has the information I give them.

Accounting is not deterministic, within certain bounds it is very subjective.