Hi Royal,

Thanks for the response.

Enter the Maximum Package Weight you will ship 30000 (I've tried 30, it makes no difference)
Package Tare Small to Medium - added percentage:weight 0:0.3
Larger packages - added packaging percentage:weight 0:0.5
Display Number of Boxes and Weight Status 3

They easily fit inside a box that is 30x25x20. I have configured all 20 boxes in SellOnline just to try and get it to work. I don't actually have predictably-sized boxes. I'm not a high volume shop so I'm recycling boxes that local shops throw away. Here are my SellOnline boxes, with two likely candidates highlighted:

Description, Weight Limit of Box(kg), Box Weight(kg), Length(cm), Width(cm), Height(cm)
100x50x50 30.000 0.500 100.0 50.0 50.0
30x30x30 30.000 0.300 30.0 30.0 30.0
60x60x60 30.000 0.500 60.0 60.0 60.0
15x15x15 30.000 0.100 15.0 15.0 15.0
100x50x50 30.000 0.500 100.0 50.0 50.0
100x30x30 30.000 0.500 100.0 30.0 30.0
100x20x20 30.000 0.500 100.0 20.0 20.0
75x50x50 30.000 0.500 75.0 50.0 50.0
75x40x40 30.000 0.500 75.0 40.0 40.0
75x30x30 30.000 0.500 75.0 30.0 30.0
75x20x20 30.000 0.500 75.0 20.0 20.0
50x40x40 30.000 0.500 50.0 40.0 40.0
50x30x30 30.000 0.500 50.0 30.0 30.0
50x20x20 30.000 0.500 50.0 20.0 20.0
25x50x50 30.000 0.500 25.0 50.0 50.0
25x40x40 30.000 0.500 25.0 40.0 40.0
25x30x30 30.000 0.500 25.0 30.0 30.0
25x20x20 30.000 0.500 25.0 20.0 20.0
50x50x50 30.000 0.500 50.0 50.0 50.0
40x40x40 30.000 0.500 40.0 40.0 40.0

I see now that my length, width and height dimensions are all entered with the smallest number first and largest number last, but Canada Post calls the length the largest dimension. I wonder if that has anything to do with it? Canada Post's code may not be smart enough to take the largest dimension as the length. I can use SQL to swap those around fairly quickly. I'll go ahead and try that in a minute.

What is being referred to by RodG here when he says "two pieces of code at work"? I'm guessing the same thing is happening to me. Canada Post is reportedly splitting my three items into two boxes, but Zen is reporting that they are being split into three. So Zen is adding the third box. This is further evidenced by the fact the shipping amount Canada Post says their server is sending back is the same as the shipping amount that Zen is reporting.

Sandy