@MVE - where to start, have spent some time using the data shown in your screenshots, including your entry anomalies and then manipulating that data by using different settings and transactions and I “can’t” recreate your situation - most puzzling however is the fact that one of your screenshots is displaying data it shouldn’t be but we will get to that
First the entry anomalies.
Taking the Payment screenshot shown in your first post.
a) There is no need to enter “qty” values, these are only required when entering Inventory Item data.
b) The “NAB Fee” should not be included in that payment transaction as the fee is not payable to the supplier.
The way you have it is this - The supplier is owed US$ 269.10 which becomes A$ 374.36. Your payment transaction shows you paying the supplier A$ 381.85, or an overpayment of 7.49. The bank fee is payable to a different supplier.
Edit : However, having just read your later posts it would appear that you are aligning the payment transaction to match the credit card statement amount, if this is correct then I understand your actions. Perhaps if I could suggest, that the fee (a purchase cost) be added to the Inventory Item so that the Inventory value reflects the landed cost - read the guide on Freight-In for more details.
c) The date of the Payment is exactly the same date as the Purchase Invoice. This generally is an incorrect usage of the Purchase Invoice as it’s designed for when the payment is made separately from the purchase. If you paying at the time of the purchase then generally a Spend Money entry is all that is required.
However, if the intention is for traceability of transactions with a supplier, then I understand the actions.
I know these aren’t resolving your issue but are just things I bumped into during my process of re-creation.
Now for your last P&L screenshot for the date 19.12.2016: that Inventory - Cost should not be there - regardless of it being the right or wrong figure.
Your report clearly displays “Cash Basis”, which means that both the Sales Invoice and the related Inventory Cost values don’t appear in the P&L until the Sales Invoice has been paid for. I can’t recreate this.
What happens to your P&L 19.12 report if you toggle it to accrual basis ?
So where to from here.
It would appear that something (which I can’t replicate) in “your” data file is causing the issue.
If other users (including myself) were having the same issue, then the forum would be screaming with posts.
If I understand it correctly, the above example is not just an isolated case but typical of similar transactions, true.
Without accessing your actual data file there’s not much more I can do so your options are
a) Create a test company and enter a minimal number of setting changes and transactions (which I could guide you with) and check the results - If the issue doesn’t re-occur then your data-file has the issue.
b) Send a private message to @lubos referencing this thread and see if he wants to run an analysis of your data-file as there maybe an underlying programming bug that is only triggered by a particular sequence…
c) Convert existing and wait until I get the final bill from the Bank and just enter the values in AU only.
PS: what version of Manger are you using and have you updated recently. Does the issue still occur after an update.