Glossary / Volume tier
Glossary
Volume tier
A rate that changes once you pass a threshold — $1.25 per carton up to 200, $0.95 after that.
What it means
A volume tier splits a charge into brackets. Each bracket has its own rate, and the bracket you land in depends on how much you did that month. Two spellings exist and they price differently: a graduated tier charges each bracket at its own rate, while a volume tier applies one rate to the whole quantity once you qualify.
What goes wrong
The tier gets billed flat. Every unit is charged at the first bracket's rate, and the cheaper brackets never apply. It is the single most common overcharge in fulfillment billing because it is invisible: the line item looks normal, the arithmetic is only wrong if you rebuild it.
The arithmetic
320 cartons, billed flat
320 × $1.25 = $400.00
320 cartons, graduated
200 × $1.25 = $250.00
120 × $0.95 = $114.00
-------
$364.00
Difference $36.00How to check it
Find the clause, find the threshold, and split your volume at it. If your invoice line equals quantity × the first rate, the tier was not applied. You can run exactly this on the home page with your own rates.