Money, sales tax and rounding between a store and an ERP

How does each system write an amount?

The same 46.29 dollars travels in five forms:

Stripe's documentation is explicit: 100 means one dollar, and 100 means 100 yen, because the yen has no decimals. An integration that reads the Stripe amount into a dollar field without dividing books a 46.29 payment as 4,629.00. The reverse, dividing a yen amount by 100, books 100 yen as 1. The rule per source is one line: integer in minor units, divided by 10 to the power of the currency's decimals.

Strings need the same care. "46.29" is read as a decimal, never as a binary float, and $1,234.50 from a file is stripped of the symbol and the comma before it is a number. More on files in supplier CSV and Excel files.

Is the tax in the price or on top?

In US stores tax is added at checkout. Shopify still sends a flag on every order, taxesIncluded, and WooCommerce sends prices_include_tax. A store that also sells to Canada or Europe can show tax-inclusive prices in those markets, so the flag is read per order and not set once per store.

When the flag is true, the line price contains tax. 21.78 with 21% included is 18.00 net; booking 21.78 as the net price in an ERP that adds tax produces a total of 26.35 for a customer who paid 21.78.

Which system calculates the sales tax?

US sales tax depends on the ship-to address, down to the city and special district. New York State's Publication 718 lists the combined rate per jurisdiction: 8⅞ percent in New York City, 8⅜ in Putnam County, 8 in counties such as Monroe and Schenectady, effective March 1, 2025. The store calculates tax at checkout, with Shopify Tax, manual rates or a tax app, and records it per line item. Each Shopify TaxLine carries a title, a rate and a priceSet with the amount.

NetSuite can calculate tax too. With legacy tax, the sales order has a header taxitem and taxrate, and NetSuite's field help describes taxtotal as the tax rate multiplied by the taxable total of the lines. Left to itself, NetSuite recalculates the tax the store already charged. Three outcomes:

With SuiteTax, the sales order has a taxdetailsoverride checkbox; NetSuite's field help says only roles with at least Edit on the Tax Details Tab permission can override. The integration role needs that permission, or the store's amounts cannot be posted.

Marketplace orders add one more case. Shopify's TaxLine.channelLiable is true when the channel that submitted the order is liable for remitting the tax. That tax belongs in the order total and not in the seller's sales tax payable.

Rounding per line or per order?

A sales tax amount is rounded to the cent. The question is when. Three lines, ordered from New York City at 8.875 percent:

Rounded per line and summed, the tax is 3.78 and the customer pays 46.29. Calculated once on 42.51, the tax is 3.77 and the invoice says 46.28. The payment of 46.29 does not match the invoice, and 0.01 sits unapplied until someone clears it. If one order in three has such a difference, a store with 2,000 orders a month has 667 payments a month to clear by hand.

The fix is not a better rounding rule in the ERP. It is to post the tax amounts the store calculated, per line, so the ERP total is the amount the card was charged. The rate goes along for reporting; the amount is what counts.

Discounts and shipping

An order-level discount has to be spread over the lines, because the ERP books revenue per line. Shopify returns its own allocation per line in discountAllocations, and totalDiscountsSet holds the order and line discounts together; the integration uses Shopify's allocation so the ERP lines match the store. Where a source sends only an order total, the integration spreads it. A 10.00 discount on the order above, spread by line value:

• 14.97 / 42.51 x 10.00 = 3.5215, rounded 3.52
• 12.49 / 42.51 x 10.00 = 2.9381, rounded 2.94
• 15.05 / 42.51 x 10.00 = 3.5404, rounded 3.54

3.52 plus 2.94 plus 3.54 is 10.00 here. With other amounts the rounded parts add up to 9.99 or 10.01, and the last line takes the difference. The unit price after the discount on line 1 is 11.45 / 3 = 3.8167, which has no exact cent value. Shopify's documentation describes discountedUnitPriceAfterAllDiscountsSet as the approximate unit price. The integration maps the line total and the quantity, never a rounded unit price times the quantity.

NetSuite has its own discount logic. The field help for the discount on a sales order: if the discount item is taxable, the discount is applied before taxes; if not, after. A taxable discount item reduces the tax base, a non-taxable one does not, and the wrong one changes the tax by 8.875 percent of the discount: 0.89 on 10.00.

Shipping has tax lines of its own in Shopify, on each ShippingLine. When the store charged tax on shipping, the NetSuite side needs shippingcost and a shippingtaxcode that produce the same amount.

Tax-exempt customers and other currencies

B2B buyers who resell are often exempt. The two systems model it differently:

NetSuite's field help adds the catch: a customer is non-taxable only if the Taxable box is clear and the Tax Item field is empty. An integration that clears the box and leaves a tax item creates a customer who is still taxed.

Currency adds a second amount to every money field. Shopify sends shopMoney in the store's currency and presentmentMoney in the currency the customer paid. NetSuite fixes a customer's currency once transactions exist for that customer, and the sales order carries an exchangerate. A Canadian customer who paid in CAD is booked in CAD with the rate of the order date, or in USD with the shop amount. The two give different revenue in the books, and the mapping states which one applies. Order dates themselves have a trap of their own, described in dates and time zones.

What this means for your integration

We map every amount with its source format, its currency and its tax treatment, and post the store's own tax amounts, so the total in your ERP is what the customer paid. Discounts are spread per line with the remainder on the last line, and exemptions are mapped per state to your ERP's customer fields.

In the dry run before go-live your recent orders pass through those rules, and every order whose ERP total differs from the store total by even a cent shows up with the line that causes it. The full field list for orders is on orders, customers and shipping, and the general method on field mapping. Tell us which store and ERP you use, and we show you where the cents go missing.