(@mackeT – Just came back tp update and saw your comment) Initially Apple did not appear to understand the issue and explained how we should calculate the %age, i.e. the way we were. On 18 June we were assured the problem was being investigated and given a case number. The June financial reports are just out and we see the same problem – in general all USD/CAD sales are at 15% and others typically 30%, sometimes 15%, and some at "23%" – which allowing for rounding is the mid-point but that might be a coincidence. We are just going to follow up under our case number. We encourage everybody to check their financial reports and raise an issue direct with Apple if this is affecting them, if enough devs raise the issue they'll probably get it fixed quicker.

@mackeT – an update. Apple are suggesting that local taxes explains the apparent 30% commission, i.e. that by coincidence that local tax rates are ~15% and previously the total take was ~45%. There appears to be some merit in that suggestion, though different localities have different tax rates. However, at least in our accounts, there are significant discrepancies such as sales in the same country on the same day being charged at total commission + tax rates of ~15% and ~30% – but maybe that is a different error. If the differences are all down to tax rates it begs the obvious question of why there isn't a "local tax %" column to make it obvious and why in the financial_report tables, which does have columns for tax, all the values are 0 – at least in our reports. We've raised that with Apple. TL;DR Apple are suggesting/hinting it is all down to fluctuating (we compared different months) tax rates and the rest is coincidence. If we get any more we'll report here.

@mackeT – Did you ever get an explanation? We've just had an response from Apple directing us to download a report which will provide all the answers... but the report isn't there to download, at least we can't find it. We've let Apple know. We think it is unlikely Apple is getting the maths wrong and they're just not being clear, but who knows...

We just came back here to report on our "progress" (see above) and saw your post. We have an open case number, the Apple person associated with it has said they see our point and Apple is working on providing the explanation… But no explanation ever arrives, just more monthly reports with inexplicable numbers. We actually suspect the calculation are correct, and we've told Apple we're happy to have "egg on our faces", but realistically we'll never know. After another couple of months of silence from Apple we've written to them to suggest they just own up and admit they'll never give us the data. They'll probably reply that they're still working on it, as they have been for half a year now, and after that we'll probably stop reminding them every few months the case is still open. Go email Apple directly, get your own case number, and if they ever tell you how they're doing the calculations please post it to the forums. We wish you luck, but don't get your hopes up.

Instead of updating here we've added a comment to Industrial Designer's post. In short Apple still haven't delivered, we don't expect them to.

@Herry12 – Thank you for your detailed steps and our apologies for not being clearer. We are at step 5, having done 1-4, which after searching the forums led to this post. If this step fails to provide (a pointer to) an answer then 6 is next on our list. Of course we're also continuing to review 1-4 and will be happy if this is an egg-on-face moment because we missed something! The app has been on the MAS for at least a decade, updated as needed by OS changes, and runs happily on Ventura.

@eskimo – Yes its sandboxed, its been in the MAS for years and we've hit the issue testing it for Sonoma. So far we've found nothing in the docs indicating a change in this area, if you can point us to this being a known change with a solution that would be great. Otherwise we'll post a bug report and raise a tech support issue as this is rather critical to the app; we're just finishing a demo of the issue (aka removing most of the apps code).