Are you getting the same error for new “Manual customer invoices” with the same values as this erroneous one? If this is repetitive, I believe this could bug that may be connected with parallel currency. If the error is only limited to the above invoice, this should be corrected from data repair.
Could you please go to the Voucher tab and check if the Balance equals 0 as highlighted below.
As mentioned above, you may report a case to IFS Support if it’s in balanced state. There have been several software faults reported in this functionality which have been fixed through bug fix - 154633(UPD 9) and 149313(UPD 6)
As per the error message, this could be due to an imbalance in your voucher. Please check your voucher details and check whether any difference is there among values of IP2 and IP4 postings.
If so, you may check whether any value is defined in below fields of your company window. As mentioned in the help text, this is the maximum acceptable debit/credit voucher difference in accounting/parallel currency when an invoice is posted.
Additionally, you will have to define IP31 Posting in your ‘posting control’ window (since this is customer invoice). This is to post any acceptable voucher differences at the point of creating the voucher.
Thereafter, you may try to cancel the invoice.
However, if you still get the error, then it would require an in-depth investigation and you will have to report it to IFS. Because, this is a common error that could occur due to various reasons. Some reasons, which are identified as bugs, are already addressed.