One AP export, two recoveries: duplicate payments and vendor sales tax

The situation

The group spends about $60M a year with suppliers across three legal entities that share many vendors. An ERP change two years earlier left duplicate vendor records. Taxable purchases run about $9M a year at a blended 7% rate, and the distributor holds resale certificates with most vendors.

What was uploaded

• Paid-invoice ledger for 24 months from the ERP (CSV, all three entities)
• Vendor master list
• Purchase lines with tax detail for 36 months
• Resale and exemption certificates on file with each vendor

What the engine found

• Duplicate payments

  $51,200

  Invoice numbers keyed two ways (for example INV-1043 and 1043) and suppliers set up twice after the ERP change.

  Rule: fuzzy_duplicate

• Same invoice paid by two entities

  $18,700

  Shared suppliers paid once by each entity for the same invoice.

  Rule: cross_entity_duplicate

• Credit memos never applied

  $21,300

  Credits sitting on supplier statements that were never taken against later invoices.

  Rule: unapplied_credit

• Payments above the invoice amount

  $5,200

  Payments that exceeded the invoiced amount after manual edits.

  Rule: overpayment

• Taxed despite a certificate on file

  $19,800

  Vendors charged sales tax on goods bought for resale while holding the distributor's certificate.

  Rule: exempt_certificate

• Rate above the expected local rate

  $5,300

  Deliveries taxed at another jurisdiction's higher rate.

  Rule: rate_above_expected

• Tax lines billed twice

  $3,600

  The same tax line appearing twice on one invoice.

  Rule: duplicate_tax_line

• Tax charged on tax

  $2,800

  Tax calculated on a total that already included tax.

  Rule: tax_on_tax

The numbers

Found

$127,900

Expected

$83,200

Recovered within 6 months

$76,800

Supplier payments: $96,400 found, $58,900 recovered. Sales tax: $31,500 found, $17,900 recovered.

What it would cost, three ways

Over the same 6 months, in USD.

Time spent

About 14 hours over six months: two exports, a review of the findings, 23 supplier letters and follow-up calls.

The lesson

Duplicate vendor records were the biggest single source of duplicate payments. Merging them, and asking each supplier for a statement of account before sending a refund request, turned most findings into credits within weeks.