This guide helps UK e-commerce managers, feed specialists and developers resolve those differences. The practical output is an identifier evidence ledger: a record of what the customer buys, who created the pack, which evidence supports the identifier and whether the proposed feed mapping is ready for approval.
Quick answer
- Confirm the sold unit and who created it before changing a GTIN. Do not guess an identifier to clear a warning.
- Distinguish manufacturer packs from identical units grouped by the retailer. Their Merchant Center mappings differ.
- For a retailer-created bundle, establish whether there is a clear main product before applying the bundle rule.
- Separate “not yet found” from “not assigned”. An empty GTIN field does not justify declaring that identifiers do not exist.
- Keep the evidence, mapping decision and unresolved exceptions together so the next import cannot silently reverse the correction.
What This Guide Does Not Solve
The scope is product identity and its representation in Google Merchant Center. It does not generate GTINs, allocate barcode numbers or provide a complete product-page writing process. Product classification here is not a substitute for advice from the brand owner or GS1 where identity or allocation responsibility is disputed.
When to Pause or Escalate
Stop the identifier change if the packaging, supplier record and sold quantity disagree. Retain the competing evidence and ask the supplier or brand owner which commercial unit each number identifies.
Pause automated propagation if one correction would overwrite several pack sizes or variants. A shared source field may be the cause of the error. Do not replace a disputed identifier across the catalogue before checking that dependency.
Describe the Sold Unit Before Reading the Barcode
Write a literal sentence describing what one purchase delivers. For example: “One sealed manufacturer pack containing six identical cloths” or “Six individually packaged cloths grouped by the retailer”. Both deliver six cloths, but they are different merchandising arrangements.
Check the selected option, product title, pack description, image and checkout quantity. Ask the fulfilment team what is picked when quantity one is ordered. A photograph showing several items is not enough to establish whether the price buys one item, one pack or several packs.
Record whether the supplier’s unit is a consumer item, a manufacturer pack or an outer case used for ordering and transport. Do not assume the barcode nearest the delivery label identifies the product offered on the website. Ask for a documented relationship between the supplier’s ordering unit and the unit being sold.
Keep the store SKU, supplier stock code, manufacturer part number and GTIN in separate fields. A SKU organises your catalogue; an MPN is a manufacturer part number. Google warns against substituting internal store values or identifiers from similar products when the correct identifier is unavailable.
Formatting checks belong after that identity work. A correctly formed number does not establish which product is inside the packaging. Passing a check-digit test can help identify a transcription problem, but cannot settle a dispute about pack quantity, brand or variant.
Apply the Rule for the Pack You Actually Created
Google’s feed attributes distinguish several arrangements that retailers may loosely call a “bundle”. Use the commercial facts to select the rule. The label in a supplier spreadsheet is supporting evidence, not the decision itself.
| Offer | Identity basis | Pack attribute treatment |
|---|---|---|
| One manufacturer-created multipack | The manufacturer’s identifiers for that pack | Do not submit multipack merely because the pack contains several units |
| Identical manufacturer-defined products grouped by the retailer | The identifiers of the product being grouped | Submit multipack with the number of those products grouped |
| A manufacturer-created bundle | The manufacturer’s identifiers for the bundle | Do not submit is_bundle for a manufacturer-defined bundle |
| A retailer-created main product with complementary accessories | The main product’s identifiers | Submit is_bundle as yes |
| A mixed retailer-created set without a clear main product | Requires separate identity review | Do not force it into the main-product bundle rule |
These are Merchant Center submission rules. They do not establish a universal barcode-allocation policy for every marketplace or trading partner. A business deciding whether to allocate a new trade-item identifier needs to resolve that separate question with the appropriate standards and brand-owner evidence.
Count the manufacturer-defined products being grouped
The multipack attribute describes retailer-created grouping. If the retailer combines three manufacturer packs, each containing two items, the attribute value is three, not six. The offer contains six items in total, but the retailer has grouped three manufacturer-defined products.
For a single manufacturer pack of six, do not add multipack=6. Record the pack quantity clearly for buyers and verify the pack’s own identity. Using the same numeric quantity everywhere can make a neat spreadsheet while describing the wrong offer.
Find the main product before using the bundle rule
Google’s retailer-bundle rule concerns a main product with complementary products sold together for one price. A camera with a carrying bag has a clearer main-product relationship than a mixed set of equally important items.
If the relationship is unclear, record why. Do not select the most expensive component or the first item in the title simply to obtain an identifier. For a manufacturer-defined set, request the manufacturer’s evidence for the complete set instead of reconstructing its identity from the components.
Build the Evidence Before Trusting the Mapping
Collect evidence close to the physical product and the organisation responsible for its identity. Useful material includes photographs of the actual packaging, a current manufacturer catalogue entry and written confirmation tying the identifier to the exact model and pack.
Supplier spreadsheets can be valuable, but check what their columns mean. A field labelled “barcode” may refer to an individual item, an ordering case or a superseded record. Record the file date and the supplier’s explanation rather than copying the value without context.
GS1 UK’s Verified by GS1 service provides a route to checking product identity against registry information. Use the returned information as an additional check. Compare the available description and company details with your evidence; if a result does not establish the pack relationship, keep that relationship unresolved.
Ask a precise question when evidence conflicts: “Does this identifier refer to one individual item, this sealed six-pack or the outer case?” Include the supplier reference and pack photographs. A reply that only repeats the disputed number does not answer the unit-of-sale question.
Hold the mapping when the number appears plausible but the evidence does not establish its relationship to the offer. Record the missing fact, who can resolve it and what document or confirmation would allow the decision to proceed.
Use an Identifier Evidence Ledger
A ledger should let another reviewer follow the decision without relying on the original editor’s memory. Use one row per offer requiring a distinct decision. Attach evidence references rather than putting whole supplier documents into the row.
| Field | What to record | Decision it supports |
|---|---|---|
| Offer identity | Store SKU, selected variant and literal sold-unit description | Which customer offer is under review? |
| Composition | Item types, quantities, packaging and who assembled the pack | Which pack or bundle rule applies? |
| Brand and manufacturer reference | Verified brand, MPN where assigned, supplier reference kept separately | Do all records refer to the same product? |
| Candidate identifier | The exact value from the source, its field label and claimed packaging level | What does the proposed number identify? |
| Evidence | Source owner, document or image reference, date and the fact supported | Can another reviewer reproduce the conclusion? |
| Feed mapping | Proposed identity fields, multipack or is_bundle decision, and rationale | How will the verified offer be represented? |
| Confidence and state | Confirmed, conflicting or incomplete evidence; ready, hold or escalate | May the proposed change proceed? |
| Ownership | Reviewer, unresolved question, responsible person and next review trigger | Who resolves and maintains the decision? |
Define “confirmed” narrowly: the evidence establishes the relevant product or pack and supports the proposed mapping. It does not mean the product will be approved by every platform or that sales will increase.
Keep confidence separate from workflow status. A mapping can be well supported but awaiting a controlled feed release. Another mapping may already be live while its evidence remains disputed. Combining both into a green “complete” flag hides the distinction.
If the ledger contains a source value and a proposed replacement, preserve both with the reason for the change. That allows a later reviewer to distinguish a corrected transcription from a change in the product being sold.
Worked Example: Two Six-Packs with Different Evidence
Hypothetical example: a retailer offers the same type of cleaning cloth in two arrangements. The products, evidence references and review findings below are invented for explanation. No actual product identifiers or client audit results are presented.
Offer A is a sealed six-pack created by the manufacturer. Offer B is six individually packaged cloths grouped by the retailer. In the fictional evidence set, PACK-A identifies the manufacturer six-pack and UNIT-B identifies the individual product used in Offer B. These are evidence labels, not GTIN values, and must never be entered into a feed.
| Offer | Evidence and issue | Proposed decision | Review state |
|---|---|---|---|
| A: one manufacturer six-pack | Packaging image A and written manufacturer confirmation identify PACK-A. Imported record currently points to an individual item. | Replace the disputed mapping with the verified pack identifiers; omit multipack. | Evidence confirmed within the hypothetical scenario; mapping ready for controlled review |
| B: six separate units grouped by retailer | Composition record B confirms six identical units. Unit packaging and manufacturer record identify UNIT-B. | Use the verified individual product identifiers and multipack=6. | Evidence confirmed within the hypothetical scenario; mapping ready for controlled review |
| C: a proposed outer-case offer | Supplier file says “case”; photograph and quantity definition are missing. | No replacement selected. Request the case contents and identifier relationship. | Incomplete; hold and escalate to supplier |
The correction is different for A and B even though each customer receives six cloths. Offer A needs evidence for the manufacturer’s pack. Offer B uses the retailer-grouping rule. The third row shows why a familiar supplier description cannot substitute for an identified unit.
As a counterexample, imagine the retailer groups two sealed manufacturer six-packs. The customer receives twelve cloths, but the retailer groups two manufacturer-defined products. Under the multipack rule, the count is two and the identity basis is the manufacturer six-pack being grouped.
The review note should therefore state both the total contents and the number of grouped products. A rule that automatically copies “twelve” from the title into multipack would be wrong for that arrangement.
Handle Own-Brand Products Without Inventing an Exemption
Own-brand status does not prove that no GTIN exists. Ask the person responsible for the brand’s product data whether an identifier has been assigned to the exact product and variant. Check the relevant packaging and records before choosing the feed treatment.
Where no GTIN has been assigned, Google’s guidance allows submission without one and points to brand and MPN where available. Keep those established identifiers accurate. Do not borrow a number from an apparently identical item sold under another brand.
An MPN is not interchangeable with a reseller’s convenient stock code. Confirm who assigned the number and which product it identifies. Decisions about assigning new identifiers are outside this audit; do not let an import script create a substitute merely because a field is empty.
Use identifier_exists=false only where the product meets the applicable no-identifier conditions and you have established that assigned identifiers do not exist. It is not a switch meaning “our spreadsheet has no GTIN”. A product with a genuine brand and MPN needs different consideration from one with no assigned identifiers.
Keep three separate ledger states: assigned and verified; assigned but not yet obtained; and confirmed not assigned. The middle state requires investigation. Collapsing it into the third state turns missing evidence into a false product claim.
Investigate Repeated Numbers Before Replacing Them
Repeated GTINs deserve review, but repetition alone does not prove an error. Google distinguishes offers using relevant attributes, including multipack. An individual item and a retailer-created group of those items can therefore use the same identity basis while describing different offers.
Compare the country, language, condition and applicable variant attributes alongside the identifier. Google’s GTIN guidance warns against duplicate product submissions with the same GTIN and the same relevant variant values. Do not “fix” a duplicate offer by inventing a different number.
A different problem occurs when unrelated colours, sizes or products inherit one number from a parent record. Trace the mapping back to its source and inspect the selected variant. Repairing one exported row may leave the inheritance rule ready to reintroduce the error on the next run.
Likewise, retain identifiers as exact recorded values during spreadsheet handling. Check imports and exports for lost leading zeros, truncated digits or scientific notation. A transformed value needs comparison with the original source, not a guessed reconstruction.
Release Corrections as Evidence-Based Changes
Prepare a small change set with the old value, proposed value, affected offers and evidence reference. Include the relevant pack attributes in the review. Checking a GTIN in isolation can miss the reason the same number is valid for one retailer-created grouping but wrong for a manufacturer pack.
Confirm that the rendered offer and checkout describe the same contents as the approved feed mapping. The selected product, title, quantity and price must make the sold unit understandable. This check concerns identity consistency; it is not a reason to rewrite unrelated product copy.
For the wider distinction between page markup and submitted product data, see how merchant listing schema and product feeds fit together. A feed correction should be reviewed alongside the page’s product identity, rather than assumed to repair every representation automatically.
After an authorised release, inspect the actual submitted values and subsequent product status. Record the result and any remaining issue. Feed acceptance shows that the submitted data passed that stage of processing; it does not replace evidence that the number belongs to the product.
Reopen the ledger when the supplier changes packaging, the pack composition changes, the brand changes or a source file replaces a previously verified value. Give unresolved exceptions an owner and review date so they do not become permanent unexplained blanks.
How to Get This Done
Gather a focused sample of disputed offers, the feed rows, packaging photographs, supplier references and the literal sold-unit descriptions. A useful review should return a mapping decision for each offer, the evidence supporting it and a clear list of questions that remain with the supplier or brand owner.
KAP SEO Services provides Google Shopping feed diagnostics covering identifiers, product data and feed consistency. Bring the conflicting evidence as well as the current warnings. The aim is to resolve what the store sells and how the feed represents it, with unresolved cases held for clarification.
Summary
The sold unit comes first. Establish its composition and who created the pack, then apply the relevant identifier and pack-attribute rules. Preserve the evidence behind each mapping, distinguish unknown from unassigned identifiers and keep conflicting cases visible until the responsible source resolves them.
Frequently Asked Questions
Can a six-pack use the single item’s GTIN?
A retailer-created group of six identical individual products follows Google’s individual-product identity rule with multipack=6. A manufacturer-created six-pack uses the manufacturer’s identifiers for that pack. Confirm which arrangement is actually sold.
Does a correct check digit prove the GTIN is right?
No. It checks a property of the number. You still need evidence that the identifier refers to the correct product, brand, variant and packaging level for the applicable feed rule.
What if the supplier provides conflicting identifiers?
Keep both values with their sources and dates. Ask the supplier or brand owner to identify the unit and packaging level attached to each. Hold the proposed correction until the conflict is resolved.
Should every own-brand product use identifier_exists=false?
No. Own-brand products may have assigned identifiers. Verify whether a GTIN, brand and MPN exist and follow the applicable requirements. A missing value in your export is not proof that no identifier has been assigned.
Should every mixed set be marked as a bundle?
No. Google’s retailer-bundle rule requires a main product with complementary products. Manufacturer bundles and mixed sets without a clear main product need the appropriate separate assessment.
Resolve the Product Identity Behind Your Feed
Bring your disputed offers, pack evidence and current feed mappings for a focused review.