Supplier Invoice Discrepancies: Quantity, Price, Tax, and Duplicates

Start with identity, not arithmetic

Before recalculating totals, confirm that the document belongs to the supplier and purchase you think it does. Shopify’s invoice-process guidance ↗ places accuracy checking and discrepancy resolution before approval and payment.

• Supplier legal or trading name
• Invoice number, invoice date, and due date
• Referenced purchase-order number
• Currency, subtotal, tax, and total
• Whether the document is an invoice, credit note, pro forma, or statement

A revised invoice may repeat a commercial charge with a new document number. A credit note should not be treated as a positive invoice. Preserve the document type and relationship instead of matching on total alone.

Quantity discrepancy

What it means: the supplier billed a quantity that does not agree with the relevant ordered or received quantity.

The invoice agrees with the order but not the current receipt. The remaining six units might be in transit, the supplier might invoice on shipment, receiving could be incomplete, or the supplier might have billed too much. The comparison identifies the exception; a person determines the cause.

What to inspect

• Partial shipments and dates
• Accepted versus rejected quantities
• Backorders
• Pack-versus-each units
• Promotional units and returns

Shopify allows partial receiving and separate shipments. Accepted inventory becomes available; rejected inventory is recorded but does not become available. See its linked-transfer receiving guidance ↗.

Unit-price discrepancy

What it means: the invoice unit price differs from the ordered PO or an approved commercial change.

Do not compare only the line total. A unit conversion can hide a mismatch: 60 each at $7 may equal 10 cases of six at $42, but only when the units are documented.

What to inspect

• Currency and exchange treatment
• Case, pack, weight, or each unit
• Quantity-break pricing
• Contract price effective date
• Discount or rebate presentation
• Approved changes and rounding precision

Shopify purchase orders store line costs, tax, and adjustments, and can reuse earlier supplier costs. Because those values remain editable, retain the ordered version and any approved change. See Shopify purchase-order fields ↗.

Tax discrepancy

What it means: the invoice and PO disagree about taxable lines, tax rate, tax amount, or whether a price includes tax.

What to inspect

• Supplier and destination jurisdiction
• Tax-inclusive versus tax-exclusive prices
• Taxable freight or fees
• Exempt products
• Credits and discounts
• Rounding by line versus at invoice level

A checker can show arithmetic and source values, but it should not decide tax treatment. Route unresolved tax exceptions to the person responsible for accounting or tax policy.

Duplicate-invoice risk

What it means: an incoming invoice resembles one already recorded strongly enough to require review.

Compare normalized supplier identity, invoice number, date, currency and total, referenced PO, and line pattern. Do not label every similar invoice a duplicate: suppliers can use recurring totals, split one PO across invoices, or issue replacements and credits. The safe outcome is “possible duplicate—review these two documents,” with both sources displayed.

Uncertain line match

An uncertain match is the correct result when the evidence does not justify certainty. Common causes include missing supplier SKUs, abbreviated descriptions, different languages, pack-size changes, one invoice line covering several PO lines, mixed freight or duty, and substituted products.

Show the strongest candidate lines and the reason for uncertainty. Never hide an unresolved match inside a high-level “invoice matched” badge.

Keep a discrepancy-resolution record

1. The invoice source line.
2. The PO source line.
3. The receiving source line, when applicable.
4. The type and amount of difference.
5. The reviewer’s disposition.
6. Any corrected invoice, credit, approved change, or receiving correction.

This structure lets another person reproduce the reasoning later. It also separates detection from authority: the checker finds and explains; the assigned employee decides.

Start with the Shopify supplier-invoice reconciliation process, or read the three-way matching explainer if the receiving record is the missing piece.