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Overview

When calculating taxes or posting transactions to Zamp, take a look at this guide for how the math works for item values and totals.
Zamp’s APIs accept up to the cent (second decimal place) for financial values. Otherwise, we will return a Number must be a multiple of 0.01 error.

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Transaction Total

At the transaction-level, the total is the aggregate of the item costs minus discounts, any shipping and / or handling, and tax collected. Zamp will validate the totals being passed on calculation and transaction posting attempts. Total=sum(lineItems.amount∗lineItems.quantity)−discounts+taxCollectedTotal = sum(lineItems.amount * lineItems.quantity) - discounts + taxCollected

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Calculating Item Cost with Discounts

  • I have a transaction for 2 of the same item.
    • They cost $10 each.
  • There is a promotion running for $10.00 off your cart. 
  • The item cost for this transaction is $10.
(10.00∗2)−10.00=10.00(10.00 * 2) - 10.00 = 10.00
  • I have a transaction where 3 different items are being sold.
    • Item A is $10, and the customer ordered 1.
    • Item B is $15, and the customer ordered 3.
    • Item C is $20, and the customer ordered 2.
  • There is an additional 20% discount for the cart.
  • The item cost for this transactions is $75.00
(10.00∗1)+(15.00∗3)+(20.00∗2)−20.00=75.00(10.00 * 1) + (15.00 * 3) + (20.00 * 2) - 20.00 = 75.00
  • I have a transaction for 3 of the same item.
    • The item costs $10.00.
  • There is a “Buy Two Get One Free” promotion, so the discount is $10.00.
  • The item cost for the transaction is still $20.00, but there is no transaction-level discount value since it is factored in at the line-item.
(10.00∗3−10.00)=20.00(10.00 * 3 - 10.00) = 20.00

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Calculating Totals

  • I have a sale with a single line item worth $20.00.
    • It costs $1.50 to ship.
    • It costs $1.00 to handle.
    • It has $2.00 of tax calculated.
  • The total for this transaction is $24.50.
20.00+1.50+1.00+2.00−total(24.50)20.00 + 1.50 + 1.00 + 2.00 - total (24.50)
  • I have a sale with 3 line items.
    • Each cost $10.00.
    • It costs $5.00 to ship AND handle.
    • The tax calculated is $3.00.
  • The total for this transaction is $38.00.
(10.00∗3)+5.00+3.00=total(38.00)(10.00 * 3) + 5.00 + 3.00 = total (38.00)