How to Choose a Diamond Wholesaler: A Supplier-Verification Checklist

A diamond wholesaler should be selected on evidence, not location, reputation alone or the lowest first quotation.

Before placing an order, verify the supplier’s legal business, authority to sell the goods, product disclosures, grading reports, sourcing documentation, prices, payment terms, fulfilment process and return procedure.

Then test the supplier through a controlled first order.

A professional-looking website, recognised address, trade membership or laboratory report can support due diligence, but none independently proves that the supplier, diamond and transaction are suitable.

Last reviewed: 6 September 2026

> Commercial disclaimer: This checklist provides general trade guidance. It does not replace legal, tax, customs, sanctions, insurance or compliance advice for a specific transaction.

Quick answer: how do you verify a diamond wholesaler?

Complete five stages:

1. Verify the business: Confirm the legal entity, representative, registration, bank account and trade references.
2. Verify the goods: Confirm diamond type, treatment status, grading report, physical identity and ownership.
3. Verify the sourcing: Review origin, supplier-warranty and sanctions documentation appropriate to the transaction.
4. Verify the terms: Put price, currency, VAT, payment, title, risk, inspection and returns in writing.
5. Verify performance: Start with a controlled order and measure availability, accuracy, delivery and problem resolution.

Do not increase order value or extend credit until the supplier has performed consistently.

Supplier verification: critical checks and performance checks

Some checks are transaction gates. Others help compare suppliers over time.

A supplier should not pass because it performs well in one category while failing a critical verification check.

1. Verify the legal business

Request:

• Full legal name
• Trading name
• Company or enterprise number
• Registered address
• Trading address
• VAT number where applicable
• Names and roles of authorised representatives
• Business telephone number
• Business email domain
• Invoice details
• Bank account in the legal business’s name

Check the entity using the official company register in its jurisdiction.

For example:

• UK companies can be checked through Companies House.
• Belgian companies can be checked through the official Crossroads Bank for Enterprises Public Search.
• EU VAT numbers can be checked through the European Commission’s VIES service.

A registry entry confirms recorded business information. It does not guarantee solvency, product quality or performance.

Resolve inconsistencies such as:

• A bank account belonging to a different company
• An invoice from an entity not previously disclosed
• A trading address unrelated to the registered business
• A representative whose role cannot be confirmed
• A recently changed company name with no explanation
• Different VAT or enterprise numbers across documents

2. Verify the person representing the supplier

Confirm that your contact is authorised to act for the verified company.

Use independently obtained contact information when checking:

• New bank instructions
• Large payment requests
• Changes of beneficiary
• Changes of invoicing entity
• Unusual delivery addresses
• Requests involving third-party payments

Do not confirm a bank-detail change by replying to the same email that announced it. Contact the business through a previously verified channel.

3. Check trade references and claimed memberships

Ask for references relevant to the proposed relationship, such as:

• Established retail clients
• Manufacturing clients
• Professional advisers
• Banks or insurers where appropriate
• Bourse or trade-association membership

Verify memberships directly with the issuing organisation.

Determine:

• Whether the exact legal entity is listed
• Whether membership is current
• Whether the member name matches the supplier
• Whether a claimed certification covers the relevant business location and activity
• Whether a person is a member individually or only works with a member company

Membership can provide useful supporting information. It does not guarantee the quality, ownership, origin or price of an individual diamond.

4. Establish what the supplier actually controls

Online inventories can contain:

• Supplier-owned stock
• Goods held on memo
• Network or virtual inventory
• Brokered diamonds
• Goods subject to prior sale
• Duplicate listings
• Stones located in another country

Ask the supplier to label each option accurately.

Before quoting your customer, confirm:

• Current availability
• Physical location
• Ownership or authority to offer the stone
• Reservation period
• Whether the price is confirmed
• Expected dispatch date
• Whether the stone must first be obtained from another supplier
• Whether substitutions require your written approval

“Listed” does not necessarily mean “available.”

5. Confirm natural, laboratory-grown and treatment disclosure

The supplier must clearly identify whether the goods are:

• Natural diamonds
• Laboratory-grown diamonds
• Treated natural diamonds
• Synthetic stones other than diamonds
• Mixed parcels

Ask which detection and screening procedures are used, particularly for:

• Melee
• Mixed-size parcels
• Recycled diamonds
• Customer trade-ins
• Unmounted stones without individual reports
• Finished jewellery containing multiple diamonds

The invoice or memo should use an accurate product description. Avoid vague descriptions such as “white stones,” “diamond goods” or “certified stones.”

Do not rely on appearance alone to distinguish natural from laboratory-grown diamonds.

6. Verify the grading report independently

For an individually graded diamond, obtain the complete report number before approving the purchase.

Use the issuing laboratory’s official service:

• GIA Report Check
• IGI Report Verification
• My HRD Antwerp

Compare:

• Report number
• Report date
• Diamond type
• Shape and cutting style
• Measurements
• Carat weight
• Colour
• Clarity
• Cut grade where applicable
• Polish
• Symmetry
• Fluorescence
• Inscriptions
• Comments
• Treatment disclosures

A PDF or screenshot should not be treated as independent verification when the laboratory provides an official database.

GIA specifically advises that current report information should be checked through Report Check rather than relying only on a shared or printed copy.

7. Match the report to the physical diamond

Finding a report in the laboratory database confirms that the laboratory record exists. It does not prove that the supplier has presented the corresponding stone.

Match the physical diamond using:

• Report-number inscription where present
• Carat weight
• Shape
• Measurements
• Proportion details
• Clarity characteristics
• Plotting diagram where included
• Comments
• Other identifying features

An inscription is useful but should not be the only identity check. Inscriptions can be difficult to examine, particularly when a diamond is mounted.

For a significant purchase, consider an independent examination before the approval or return period expires.

For complete report guidance, read the Diamond Grading Report Guide. For laboratory-specific differences, see GIA vs IGI vs HRD.

8. Inspect the actual diamond

A grading report does not fully communicate visual appearance.

Review:

• Face-up dimensions
• Brightness
• Contrast
• Fire
• Scintillation
• Transparency
• Inclusion visibility
• Inclusion position
• Potential durability concerns
• Girdle condition
• Bow-tie effect in relevant elongated shapes
• Windowing in step cuts
• Fluorescence where relevant
• Symmetry visible to the eye
• Overall suitability for the intended setting

For remote transactions, request representative videos and images. Confirm that media shows the exact diamond rather than a sample of the same shape and grade.

The supplier should disclose when imagery is illustrative.

9. Check parcel consistency

Parcels, matched pairs and production diamonds require different checks from an individual centre stone.

For parcels, define:

• Number of stones
• Total carat weight
• Individual size range
• Millimetre tolerance
• Colour range
• Clarity range
• Make or cut consistency
• Fluorescence policy
• Treatment policy
• Natural or laboratory-grown status
• Matching standard
• Screening method
• Replacement process
• Replenishment capability

For matched pairs, compare:

• Individual carat weights
• Measurements
• Outline
• Length-to-width ratio
• Colour
• Clarity
• Cut style
• Facet pattern
• Fluorescence
• Visual performance

Two stones with similar report grades are not automatically a matched pair.

For production requirements, use the Calibrated Diamonds Wholesale Guide.

10. Verify sourcing and origin statements

Keep these concepts separate:

• Supplier location
• Trading location
• Country of polishing
• Laboratory location
• Mining origin
• Customs origin
• Chain of custody

A supplier based in Antwerp does not prove that the diamond was mined in Belgium. A diamond polished in India was not necessarily mined there.

Ask the supplier:

• What origin information is available?
• What evidence supports it?
• What is stated on the invoice?
• Which System of Warranties statement is used?
• What sanctions checks have been completed?
• Does the shipment require additional traceability evidence?
• Can the documentation be connected to the specific stone or parcel?

The World Diamond Council System of Warranties uses warranty statements on B2B invoices and memos as part of an industry self-regulation framework.

A warranty statement is useful documentation. It does not eliminate the buyer’s own risk-based due diligence or prove every wider ethical claim.

11. Check responsible-sourcing claims carefully

If a supplier claims to be:

• Responsibly sourced
• Ethical
• Conflict-free
• Fully traceable
• Mine-to-market
• Recycled
• RJC-certified
• Chain-of-custody certified

Ask for:

• The exact definition being used
• The entity covered
• Certification number
• Current status
• Certification scope
• Included locations
• Included materials
• Supporting records for the goods
• Applicable exclusions

The Responsible Jewellery Council describes due diligence as an ongoing process rather than a one-time statement. Check any claimed status through current RJC resources.

Do not convert company-level membership into an unsupported product-level provenance claim.

12. Review sanctions and regulatory documentation

Requirements depend on:

• Buyer and seller jurisdictions
• Diamond type
• Rough or polished status
• Individual stone weight
• Mining or manufacturing origin
• Processing history
• Shipping route
• Import destination
• Transaction date

A laboratory grading report is not a sanctions certificate.

Before cross-border purchases, verify the current requirements applying to the transaction. For European buyers, use the EU Diamond Sanctions Compliance Checklist.

Where origin cannot be substantiated to the required standard, pause the transaction rather than accepting a verbal assurance.

13. Compare equivalent quotations

A larger discount does not automatically mean a better diamond or transaction.

Compare quotations using the same:

• Diamond type
• Shape
• Carat weight
• Measurements
• Colour and clarity
• Laboratory
• Cut and finish characteristics
• Fluorescence
• Treatment status
• Origin-documentation standard
• Currency
• VAT treatment
• Payment timing
• Delivery method
• Return rights

Calculate the complete acquisition cost:

Complete acquisition cost \=

Diamond price

• currency conversion
• bank charges
• shipping
• insurance
• customs or brokerage
• applicable taxes
• inspection
• return exposure
• financing cost
• setting or modification
• staff time
• inventory-holding risk

For detailed trade-pricing terminology, read Diamond Wholesale Pricing Explained.

14. Put the quotation in writing

A complete quotation should identify:

• Supplier’s legal entity
• Buyer’s legal entity
• Diamond or parcel description
• Report number where applicable
• Quantity
• Individual and total carat weight
• Price
• Currency
• VAT treatment
• Quote-expiry time
• Availability status
• Reservation conditions
• Payment schedule
• Delivery charge
• Insurance responsibility
• Expected dispatch date
• Inspection period
• Return conditions

Do not rely on a screenshot of a price without identifying the exact stone and terms.

15. Verify payment terms

Before payment, establish:

• Deposit amount
• Balance due date
• Accepted payment method
• Bank beneficiary
• Currency
• Bank charges
• Credit terms
• Late-payment terms
• Refund method
• Refund currency
• When title passes
• Whether payment reserves the stone
• What happens if the supplier cannot fulfil the order

High-pressure requests for irreversible payment before basic verification are a warning sign.

Avoid split payments, third-party beneficiaries and unexplained personal accounts.

16. Understand purchase, memo and consignment

A supplier may offer:

• Outright purchase
• Memo
• Consignment
• Brokered supply
• Customer-specific sourcing

For memo or consignment goods, document:

• Legal owner
• Possession date
• Agreed value
• Approval period
• Return deadline
• Insurance responsibility
• Permitted movements
• Whether setting or alteration is allowed
• Risk of loss
• When title passes
• Payment deadline
• Procedure for damage or loss

Never assume that goods in your possession belong to your business.

For the complete comparison, read Diamond Memo Goods and Consignment.

17. Test availability and reservation accuracy

Ask the supplier to distinguish between:

• Available now
• Available subject to confirmation
• Reserved
• On memo elsewhere
• Located with a network supplier
• In transit
• Sold
• Custom sourcing required

A reservation confirmation should state:

• Exact stone or parcel
• Report number
• Confirmed price
• Reservation-expiry time
• Deposit requirement
• Conditions that cancel the reservation

Track how often the supplier presents unavailable goods. Frequent “sold” responses after confirming availability can damage customer-facing quotations.

18. Evaluate sourcing capability

A sourcing supplier should translate a clear brief into relevant options.

Test whether the supplier can work with:

• Narrow measurements
• Specific proportions
• Fancy shapes
• Matched pairs
• Calibrated goods
• Fancy colours
• Older cuts
• Replacement stones
• Production parcels
• Customer-specific deadlines

The supplier should clearly distinguish:

• Goods it currently owns
• Goods available through its network
• Goods requiring an open search
• Specifications that may be unrealistic
• Estimated rather than confirmed prices
• Estimated rather than confirmed delivery dates

Do not interpret access to a large virtual inventory as proof of immediate fulfilment.

19. Agree the fulfilment process

Before ordering, document:

• Order-acceptance process
• Reservation confirmation
• Expected dispatch date
• Partial-shipment policy
• Substitution policy
• Packaging method
• Required documents
• Shipment value
• Courier
• Tracking process
• Delivery signature
• Delay-notification procedure
• Cancellation rules
• Contact responsible for problems

No stone should be substituted without the buyer’s approval.

The report number, invoice, packing record and physical diamond must remain connected throughout fulfilment.

20. Confirm secure shipping and insurance

Ask:

• Who arranges transport?
• When does risk transfer?
• Is the courier authorised to carry diamonds?
• What is the insurance limit?
• Does coverage apply to loose diamonds?
• Does coverage apply throughout the route?
• Are unattended-vehicle or overnight exclusions relevant?
• Is declared value required?
• Who makes a loss or damage claim?
• What evidence is required?
• Who pays return shipping?

Do not assume that standard courier compensation covers high-value diamonds.

For collection, use an authorised-person list and written handover record.

21. Put the inspection period in writing

The buyer should know:

• When the inspection period starts
• How long it lasts
• Whether weekends or holidays count
• Whether the diamond may be shown to a customer
• Whether an independent inspection is allowed
• Whether the diamond may be removed from sealed packaging
• What constitutes acceptance
• How discrepancies must be reported
• Whether setting or alteration ends return rights

The inspection window should be long enough to complete the agreed checks.

22. Verify the return policy before ordering

Confirm:

• Which goods are returnable
• Which sales are final
• Return deadline
• Required authorisation
• Required packaging
• Condition requirements
• Whether the original report must be returned
• Responsibility for shipping and insurance
• Restocking or administration fees
• Treatment of currency differences
• VAT or customs consequences
• Refund timing
• Credit-note procedure
• What happens when goods do not match their description

Custom-sourced, altered, engraved, set or specially manufactured goods may have different return terms. These must be disclosed before the order is placed.

23. Agree a discrepancy process

The written process should cover:

• Report mismatch
• Wrong diamond
• Incorrect carat weight
• Incorrect parcel count
• Undisclosed treatment
• Natural/laboratory-grown discrepancy
• Damage
• Missing report
• Late delivery
• Unapproved substitution
• Missing origin documentation
• Price or invoice error

Record:

1. Who must be contacted
2. Required photographs or evidence
3. Response deadline
4. Whether the goods must remain sealed
5. Return instructions
6. Replacement or refund procedure
7. Responsibility for related costs

A supplier’s response to a genuine problem is one of the most useful performance tests.

24. Run a controlled pilot order

Do not move substantial purchasing volume to an untested supplier immediately.

Start with an order that allows you to evaluate:

• Quote accuracy
• Availability accuracy
• Product description
• Report verification
• Visual quality
• Documentation
• Packaging
• Delivery time
• Communication
• Invoice accuracy
• Return handling

The pilot must still be commercially real. A supplier may handle a free sample differently from a normal paid transaction.

Complete more than one controlled order before treating a new supplier as a primary source.

25. Track supplier performance

Use a consistent scorecard.

Record actual performance rather than relying on general impressions.

Supplier warning signs

Pause or reject the onboarding if:

• The legal entity cannot be verified.
• Bank details do not match the supplier.
• The representative’s authority is unclear.
• The supplier refuses to provide report numbers.
• Laboratory records differ from the supplied reports.
• The diamond does not match its report.
• Natural or laboratory-grown status is unclear.
• Treatment disclosure is missing.
• Origin claims have no supporting records.
• A trading location is presented as mining origin.
• Availability is repeatedly inaccurate.
• Prices change after the order is accepted.
• Substitutions are made without approval.
• Return terms are entirely verbal.
• Shipping insurance is unclear.
• The supplier pressures the buyer to pay before verification.
• Bank instructions suddenly change.
• The invoice omits the diamond or report identity.
• The supplier requests customs undervaluation.
• Discrepancies are dismissed rather than investigated.
• Every diamond is described as perfect or investment-grade.
• The supplier guarantees resale value or appreciation.

Supplier-verification checklist

Business

• Legal name verified
• Registration number verified
• Registered and trading addresses checked
• VAT number checked where applicable
• Representative’s authority confirmed
• Bank account independently verified
• Trade references checked
• Membership claims verified directly

Goods

• Ownership or authority to sell confirmed
• Physical location confirmed
• Natural or laboratory-grown status disclosed
• Treatments disclosed
• Report verified through the laboratory
• Report matched to the physical stone
• Images and video confirmed as showing the exact stone
• Parcel quantity and weights checked
• Matched or calibrated requirements documented

Sourcing

• Supplier-warranty wording reviewed
• Origin claims supported
• Trading location not confused with mining origin
• Sanctions documentation reviewed
• Customs requirements checked
• Responsible-sourcing claims verified
• Records linked to the stone or parcel

Commercial terms

• Price confirmed
• Currency confirmed
• VAT treatment confirmed
• Quote expiry recorded
• Reservation period recorded
• Deposit and balance terms recorded
• Title-transfer point recorded
• Risk-transfer point recorded
• Memo or consignment terms signed where applicable
• No unapproved substitution allowed

Fulfilment

• Dispatch date confirmed
• Delivery destination confirmed
• Packing requirements confirmed
• Report and invoice requirements confirmed
• Courier suitability checked
• Insurance limit confirmed
• Tracking and signature required
• Delay procedure agreed

Inspection and returns

• Inspection period confirmed
• Independent inspection permitted
• Returnable and final-sale goods identified
• Return deadline confirmed
• Shipping and insurance responsibility confirmed
• Restocking fees disclosed
• Refund timing agreed
• Discrepancy procedure agreed

Performance

• Pilot order completed
• Product matched the order
• Documents were complete
• Delivery was on time
• Communication was accurate
• Any problem was resolved correctly
• Supplier approved for appropriate order level
• Next review date recorded

Frequently asked questions

Choose evidence and repeatable performance

A reliable wholesaler is not defined by one attractive diamond or one low quotation.

The supplier must repeatedly demonstrate:

• Verifiable business identity
• Accurate product disclosure
• Authentic reports matched to the goods
• Defensible sourcing information
• Clear pricing and written terms
• Realistic availability
• Controlled fulfilment
• Secure delivery
• Workable inspection and returns
• Accurate problem resolution
• Retrievable records

Complete the critical checks before the first order, test the relationship through controlled transactions and increase exposure only after consistent performance.

To review documented natural-diamond inventory or submit a trade sourcing request, browse the Dalila Diamonds inventory and provide the required shape, carat range, measurements, quality, laboratory, budget, delivery destination and deadline.