Costco Code CST-TAX: Tax discrepancy deduction (sales/excise tax adjustment).
Costco Tax Discrepancy Deductions adjust sales, local, or excise tax amounts billed on supplier invoices where Costco holds tax-exempt resale status or where tax calculations differed between vendor ERP and Costco AP systems.
Why Costco issues Code CST-TAX.
- Tax billed on a wholesale resale order where Costco provided an exemption certificate
- Tax rate calculation error on EDI 810 invoice
Documents that win.
- Valid resale / tax exemption certificates
- Original Purchase Order and Invoice
- Tax jurisdiction breakdown
How to dispute it.
Find remittance line for Code CST-TAX in Costco Depot Accounts Payable. Note the PO, invoice number, and claim amount.
Collect and verify documentation: Valid resale / tax exemption certificates, Original Purchase Order and Invoice, Tax jurisdiction breakdown. Ensure piece counts and timestamps match.
File dispute claim package via Costco Vendor Portal selecting claim reason for Code CST-TAX (Tax discrepancy deduction (sales/excise tax adjustment)) and attaching all verification documents.
Monitor claim status in Costco Vendor Portal until approved (30-45 days). Approved credit memo will apply to a future settlement remittance.
Dispute within 6 to 12 months of deduction issuance. Check your remaining filing window with our free Dispute deadline checker.
Source: Costco supplier guidance · Verified by Laxmi Narayan · 2026We audit remittances, assemble proof documents, and handle end-to-end Costco deduction recovery on pure contingency. We'll check whether yours is disputable, free, in 72 hours.