One thing about Peppol is how worryingly complex it is. I really hope it will be lobbied out in favor of a simpler solution.
As a reminder... remember the structured communication in your Belgian bank transfers? The one with triple pluses at the beginning and at the end? Like +++250/4171/01095+++.
The below shell script generates a unique one from today's year, month, day, hour and minute.
Things should not be more complex that they need be.'
DATE=date +"%y%m%d%H%M"
CHECKSUM=printf "%02d" $((DATE%97?DATE%97:97))
echo $DATE$CHECKSUM |\
sed -e 's#\([0-9]\{3\}\)\([0-9]\{4\}\)\([0-9]\{5\}\)#+++\1/\2/\3+++#'