Hi,
Here are the rules that we used when POA was designed and the logic behind it.
You can receive merchandise in POA as a delivery note, but you need to add the misc charge line (even if they are unknown) as an estimate or as a zero amount at the time of receipting the merchandise. If the link (misc charge line item) isn't established at the time of receipt, you cannot link up later.
If the miscellaneous charges have an established link to an existing delivery note (at the time of the receipt), then the rest of the miscellaneous charges, say shipping, customs, and duties, will link up and distribute to the stock on hand, when each of the misc charge invoices are received and entered. This means the "after receipt" adjustment to the estimate or zero amount of the misc charge will distribute back to the original receipts.
If the miscellaneous charges are to the same vendor, as is in prepaid freight being added to the vendors invoice, you can add it to the invoice (adjustment) as an additional line misc. charge, and it will also prorate back to the receipted items.
However, the misc charge situations you are describing relate to 3rd party charges, so you would be better to add either at the time of creating the PO as estimates or a zero amounts assigned to another vendor or at the time of receipts.
There is a switch setting in the Company Profile - Interface Options, Allow Vendor Change on Invoices, that can also be enabled, that will allow you to define a dummy vendor for miscellaneous charges(if not known at the time of creating PO or receiving), that will allow you to retroactively change the vendor to the correct 3rd party vendor (now known when their invoice arrives).
The only issue not addressed by these options is that the ability to prorate the miscellaneous charges adjustments between the amount of items of the receipt still on hand vs now sold, is not still available in POA. Currently, all prorated adjustments allocate to remaining stock on hand. So our preference and recommendation is to use estimated values for your miscellaneous charges (on PO's)to minimize the effects to residual cost values of inventory items.
Brian