Vendor Double-Billed Us: What to Do Next

You’re reviewing invoices and notice the vendor sent two invoices for the same thing. Or worse—you already paid both. Whether it’s an honest mistake or something more concerning, here’s how to handle vendor double billing.

First: Confirm It’s Actually a Double Bill

Before contacting the vendor, make sure you’re actually looking at duplicate charges.

Check for Legitimate Reasons

Partial shipments One invoice for items shipped immediately, another for backordered items. Same PO, different invoices.

Progress billing For services or projects, vendors may bill in stages. Invoice #1 might be for design, Invoice #2 for development.

Amended invoices The second invoice might be a correction to the first, not an additional charge. Look for “Revised” or “Amended” notations.

Recurring charges Monthly or quarterly invoices can look identical. Verify the service periods don’t overlap.

What to Compare

True Duplicate Indicators

You likely have a double bill if:

• Same invoice number sent twice
• Identical line items for the same service period
• Same work/delivery described on different invoice numbers
• Total exactly matches a previous invoice for identical items

Step 2: Gather Your Documentation

Before contacting the vendor, compile:

Invoice Documentation

• Both invoices (original copies)
• Any related purchase orders
• Receiving documents or service confirmations
• Contract or agreement (for service period reference)

Payment Documentation

• Payment confirmation for first invoice (if paid)
• Any pending payment status for second invoice
• Bank statements showing the payment(s)

Communication Records

• Emails related to the order or project
• Notes from vendor calls
• Any previous billing disputes

Step 3: Contact the Vendor

Reach out to the vendor’s billing or AR department. Be factual and professional—most double billing is unintentional.

Sample Email

Subject: Billing Inquiry - Duplicate Invoices [Invoice #s]

Dear [Vendor Billing Contact],

I’m writing regarding what appears to be duplicate billing on our account.

Invoice 1: - Invoice #: [Number] - Date: [Date] - Amount: [$X] - Description: [Brief description]

Invoice 2: - Invoice #: [Number] - Date: [Date] - Amount: [$X] - Description: [Brief description]

Both invoices appear to be for [the same shipment/service/work]. Could you please review and confirm whether this is a duplicate billing situation?

If this is a duplicate, please: - Issue a credit memo for Invoice #[X] - Confirm our account balance after the adjustment

[If already paid both]: We have already paid both invoices. Please process a refund of [$X] or apply a credit to our account.

I’ve attached copies of both invoices for your reference. Please let me know if you need any additional information.

Thank you for your prompt attention to this matter.

What to Request

• If unpaid: Credit memo to cancel the duplicate invoice
• If paid once: Confirmation of which invoice to disregard
• If paid twice: Refund or account credit for the overpayment

Step 4: Follow Up and Document

Track Your Request

Create a record: Vendor: [Name] Issue: Double billing Invoices Involved: [#s] Duplicate Amount: [$X] Date Reported: [Date] Vendor Contact: [Name/Email] Expected Resolution: [Credit memo / Refund / etc.] Status: [Open]

Follow-Up Timeline

• 24-48 hours: Vendor should acknowledge receipt
• 3-5 business days: Expect investigation results
• 7-10 business days: Credit memo or refund should be processed
• 14+ days: Escalate if no resolution

If You Already Paid Both

Add urgency to your follow-up. Money already out the door deserves faster attention than a billing question.

Handling Vendor Pushback

Most vendors will quickly correct double billing. Occasionally, you’ll encounter resistance.

“We don’t show a duplicate”

Your response: Provide both invoices side by side with the matching details highlighted. Ask them to confirm what distinguishes the two charges.

“These are for different items”

Your response: Request detailed backup showing what each invoice covers. If they can’t provide differentiation, it’s likely a duplicate.

“Our records show only one invoice”

Your response: Send copies of both invoices with your payment record showing you received (or paid) both.

“This was already resolved”

Your response: Ask for the credit memo or refund documentation. If they can’t provide it, it wasn’t resolved.

When Double Billing Becomes a Pattern

One duplicate invoice is a mistake. Multiple duplicates from the same vendor is a problem.

Track Vendor History

Note which vendors have billing issues: - Date of each incident - Amount involved - How it was resolved - Time to resolution

Escalate Repeat Offenders

If a vendor repeatedly double-bills:

1. Raise the issue with your account manager
2. Request process improvements on their end
3. Consider requiring detailed backup with every invoice
4. For severe cases, evaluate alternative vendors

Consider the Source

Repeated billing errors might indicate: - Poor billing systems at the vendor - Staff turnover or training issues - Intentional padding (rare but possible) - Communication gaps in your own purchasing process

Preventing Future Double Billing

Your Side

Implement duplicate detection Your AP system should flag invoices that match: - Same vendor + same amount + similar date - Same invoice number (exact or variations) - Same PO number with same line items

Three-way matching Match invoices to POs and receiving documents. A true duplicate won’t have a second receiving record.

Vendor statement reconciliation Monthly statement reconciliation catches duplicate billings you might otherwise miss.

Vendor Side

Request unique invoice numbers Ask vendors to use a consistent, sequential numbering system.

Clarify amendment process Ask vendors to clearly mark amended invoices and reference the original.

Consolidate contacts Having multiple people at your company order from the same vendor increases confusion. Designate a primary contact.

Controlled Intake

When invoices arrive through multiple channels—email, mail, portal, fax—duplicates are more likely to slip through. A single invoice submission channel for each vendor reduces confusion on both sides.

Key Takeaways

• Verify it’s actually a duplicate before contacting the vendor
• Document everything and be specific in your dispute
• Most double billing is accidental—approach it professionally
• Track vendors with repeated issues
• Implement duplicate detection to catch problems before payment

Want to catch duplicate invoices automatically? See how BillerPlus detects duplicates at submission time →