Alternate Part Approval Control: BOM, MRP and Lot Traceability

When a factory looks for an alternate part approval process, adding one approval checkbox is not enough. A substitute proposed by procurement may fit one product but not another customer, site, revision, date, or receiving lot. Planning must not treat a candidate as usable before its conditions are met. The shop floor must verify the actual part and lot, not merely copy the planned material. This guide turns engineering, QA, purchasing, planning, warehouse and MES decisions into an RFP and FAT/SAT test set for plants in Thailand. It describes a recommended control design, not a guarantee that every ERP product provides these capabilities as standard.

Alternate part approval means controlling where and when a part may be used

An alternate is more than another stock code that fits in the same space. Mechanical and electrical specifications, material declarations, customer requirements, tooling, process settings, inspection and supplier evidence can all affect acceptance. Approval must state the parent product and BOM revision, customer, site, effective period, quantity limit, supplier and affected orders. A candidate can be technically equivalent yet still be unapproved for production. Matching manufacturer numbers do not by themselves prove that packaging, manufacturing site or lot-level quality status is identical.

Keep five records distinct. A candidate is under evaluation and should not enter normal planning. Engineering fit records the tested design and process conditions. Quality acceptance records inspections, evidence, customer conditions and any hold. Authorization to use specifies the applicable product, BOM line, site, customer and effective conditions. Actual consumption records what physically went into a production order. A single “approved” flag cannot express “engineering approved, customer response pending” or “approved at Plant T but not Plant U.”

Microsoft Dynamics 365 Supply Chain Management documents plan groups and priorities for substitute items in BOMs and formulas. Master planning can prefer an available item and consider a substitute when the preferred material cannot cover demand. That is a product-specific planning mechanism; it does not, by itself, prove that every customer, QA and lot condition has been checked. Treat approval of an alternate relationship and permission to consume a particular lot on a particular order as separate decisions. Check version and feature prerequisites against the installed product. See Microsoft’s item substitution documentation.

Candidate, approved relationship and release to a work order are different

Registering a candidate creates an option. Approval allows it under stated conditions. Release to a work order confirms that the order and the received lot meet those conditions now. An approved alternate can be allowed for Customer A but prohibited for Customer B. An approved material lot can still be blocked by incoming inspection. If a one-off deviation is necessary, keep its order, quantity, authorizer and expiry separate from a permanent BOM change. The terminal’s “usable” result should reflect all three levels.

Separate parallel alternatives from engineering replacement

If two parts remain approved in parallel, the design centers on preference and use conditions. If a new part replaces an old one, the design also needs a switch date, old inventory disposition and treatment of released orders and work in progress. Microsoft describes BOM and formula version validity by period, quantity, site and product dimensions, as well as distinct approval and activation concepts. These are Dynamics examples, not universal ERP behavior. Write the boundary tests in the RFP independently of vendor names. See Microsoft’s BOM and formula version guidance.

An approval flow that separates engineering, QA, procurement and planning

A useful sequence has eight stages: request, engineering evaluation, quality evaluation, sourcing evaluation, impact approval, activation, consumption verification and expiry. Departments may be named differently, but responsibility must be explicit. Define delegate authority, segregation of duties and how a rejected or returned request is handled. A request should carry the original and candidate item IDs, manufacturer and supplier, drawing and specification revisions, material declarations, test evidence, customer limits, reason for change and intended effective date. Do not let a missing evidence package be turned into approval by clicking a button.

One person should not be able to propose the alternate, approve the engineering evidence, release a QA hold and issue the material without compensating review. Smaller plants may need a documented delegate and management review rather than complete separation. The goal is to know who saw which evidence and when. Our production system access-control guide discusses role design and audit logs. The approval screen matters less than an immutable connection between the decision, its conditions and the evidence reviewed.

Customer approval has its own state

A drawing, contract or quality agreement may require customer notice or approval before substitution. Record separately whether it is required, whether it has been received, and the exact customer, product and revision it covers. Internal approval does not authorize production if customer approval is outstanding. Microsoft’s engineering change order guidance includes fields for customer approval required and received, but automatic enforcement depends on the implementation. Test the pending-customer state in the RFP demonstration.

Keep emergency deviations narrow

A plant may allow a controlled, one-time deviation during a shortage. Record a deviation ID, reason, approver, order, lot, quantity ceiling, deadline, additional inspection and customer consent when required. Prevent the same ID from being reused on a different order. A one-off permit must not silently become a permanent approved alternate. Local contract and regulatory requirements determine whether a deviation is available at all.

Representing alternates across BOM, MRP, ERP and MES

If approval lives only in a spreadsheet while the ERP BOM contains only the original part, MRP may purchase more of the scarce original while production uses something else. Conversely, putting an unapproved candidate into an executable BOM may allow planning to select it too early. Agree on the system of record and the point at which an approved relationship reaches planning, procurement, inventory and MES. For the wider issue of BOM and inventory master freshness, see our MRP system and master data guide. Here the scope is conditional alternate authorization and actual usage.

These ownership choices are examples. A factory may own engineering BOM in PLM, manufacturing BOM in ERP and consumption events in MES. What matters is assigning one authority to each decision and avoiding independently editable “truths” in two systems. Our ERP–production management integration guide covers data contracts, retries and cancellation that also matter to alternate approval propagation.

Planned choice is not physical consumption

MRP proposes which material can cover demand based on its configured rules. The received lot can be put on hold, a reel can be changed, or the line can switch orders. A planning result must not be booked automatically as physical consumption. If planned item A, issued item B and scanned item C differ, the system should show when and why the permission was reevaluated. Ask vendors to demonstrate substitute selection during planning, order firming, warehouse issue and actual scan separately.

Effective dates alone are insufficient

Consider original and alternate IDs, parent product or BOM line, product/BOM revision, customer, site, valid-from and valid-to, quantity limit, supplier, quality state, approval evidence, reason for change and expiry rule. Not every field will matter to every plant. Even a single-site factory should make “no customer restriction” explicit. Decide whether the version freezes at order release, material issue or physical use, and define how already-released orders are reevaluated at a change boundary. A date value alone cannot resolve that question.

Quantity conversions, yield and total cost

Not every alternate is a one-for-one replacement. A candidate may use two pieces where the original uses one; units might be boxes versus pieces or weight versus length. Confirm conversion, rounding, minimum issue quantity and yield before MRP can calculate requirements. The two-for-one case is an illustration, not a claim about any product. Unit price alone misses quantity, scrap, freight, inspection and cost variances. Keep the procurement assumptions and actual consumption available for comparison.

Stop wrong-part consumption and retain actual-lot genealogy

An approved list cannot prove that the reel or box physically at the line is the right one. At a barcode or 2D-code scan, check item, lot, quality status, work order, operation, equipment, BOM revision and remaining allowance. If a check fails, show a clear reason and prevent issue or consumption at the defined control point. If offline work is unavoidable, specify the locally cached rule version, expiry, restricted override authority and duplicate-safe resynchronization. Where the system cannot physically interlock a process, specify who quarantines affected output and when.

Record an actual event such as “item B, receipt lot L, quantity Q, consumed on operation P of order O at time T,” rather than copying “part A was authorized.” Preserve a correction as a new linked event instead of silently deleting the original. Microsoft’s electronic batch records documentation describes queries for the BOM/formula version, planned and actual ingredients, substitutions, batch attributes and quality orders. This is a product example. Request equivalent query and export results from the system under consideration.

GS1 EPCIS/CBV 2.0 offers a common event language for what, when, where, why and how an identified object moved or changed state. It can inform exchange of lot and logistics events across organizations. It does not prescribe an ERP approval workflow or BOM design. Connect the alternate approval ID, consumed lot, finished lot and shipment using your own data model, and choose a sharing format that matches partner requirements. See GS1’s EPCIS overview.

The minimum two-way genealogy

From a finished lot, retrieve the work order, BOM revision, actual component item and lot, supplier lot and applicable approval. From a suspect alternate lot, retrieve all affected finished lots, on-hand stock and shipped orders or customers. Preserve every input in a many-to-one batch, and represent splits, rework and returns as separate linked events. GS1’s Global Traceability Standard provides identification and recording principles; the granularity required at a particular plant depends on product risk, contracts and applicable rules.

QA holds and revocations

An approved alternate lot still cannot be used while its incoming inspection is pending if the site’s rule requires a release. Microsoft quality-order documentation describes inspections linked to purchase, production and quarantine references. Define pending, passed, failed and conditional-release states and how each affects inventory. When an approval is revoked, stop future planning and untouched orders, identify issued material and WIP, and search already consumed and shipped lots. Do not erase prior-use history when closing an authorization.

Thailand-specific boundaries: headquarters, local plant and supplier

A Thailand site may receive product design and customer contract rules from a headquarters abroad while local staff buy and inspect material. Headquarters approval is not automatically valid at every customer and site. Names translated into Japanese, Thai and English may differ, so use stable internal item and manufacturer IDs as matching keys rather than display names. Include the time-zone offset in effective timestamps and test overnight planning at the ICT date boundary.

For imported materials, supplier, manufacturer, country of origin and actual manufacturing location may differ between purchase and receipt. Decide whether approval covers the manufacturer, the site or the specific source and lot. If original and substitute parts may be mixed in a finished batch, QA must decide whether that is allowed and what unit of genealogy is required. Avoid asserting one blanket Thai legal requirement: check each customer specification, export market and product category.

Approval service levels across sites

When headquarters engineering approval must arrive before local production can proceed, set a target for first response, escalation, missing evidence and absence of an approver. A late approval must not be converted into a green “usable” status. Planning should compare alternatives such as expedited supply, resequencing or customer-date changes. Measure the target against actual response times and revise it; it is an operating target rather than an implied contractual guarantee.

What to specify in an alternate-part management RFP

“Stores substitute parts” and “has an approval workflow” are too vague for vendor comparison. Give each bidder the same master data and rejection scenarios, and ask whether the result comes from standard features, configuration, extension, integration or manual procedure. Document constraints and additional costs. The business acceptance outcome can be common even when one architecture embeds approval in ERP and another uses a separate approval service.

A data contract needs the conditions, not only an approval ID

Sending only an approval ID to MES does not give it enough information to decide whether that approval applies to this order and lot. Send the necessary conditions, revision, effective time and revocation, or call an authoritative decision API. Use versions or event IDs to handle duplicates and ordering, not only an update timestamp. Define the behavior when a terminal cannot receive the latest rule. A local “approved” cache should not stay valid indefinitely after a revocation.

Compare the full implementation cost

A standard substitute group may cover planning but not customer-specific limits, QA holds or lot-level reverse traceability. Compare master cleanup, current-BOM review, migration of approval evidence, terminals and labels, interfaces, FAT/SAT, training, support and recovery. Ask whether a successful demo uses the standard release or a one-off extension. Use actual change volumes, rework time and affected-lot counts if estimating a business case; state assumptions and sensitivities. No market price or return percentage is invented here.

FAT/SAT cases for alternate part approval

Factory acceptance testing should use cases with predetermined expected outcomes, including refusal cases. Site acceptance testing repeats them with local items, BOMs, labels, devices, network and permissions. The IDs, dates and counts below are illustrative assumptions, not real customer data.

• Normal approval: Candidate B for original A on product P/BOM V1 moves through engineering, QA and purchasing; customer approval is obtained if needed. B is excluded from planning, orders and issue until all required gates pass.
• Site restriction: B is usable at Thailand Plant T and prohibited at Plant U. The result changes when the same order context is moved between sites.
• Revision boundary: B applies only to BOM V2. Old released order O1 using V1 is not silently overwritten; new order O2 using V2 can select B.
• Time boundary: Assume an effective instant of 15 October at 08:00 ICT. Test 07:59, 08:00, a headquarters display in another time zone and the overnight MRP batch.
• Quantity cap: Assume a one-time limit of 300 pieces. After 299 have been consumed, the next one is allowed and the one after that is rejected. Cancellation and retry must not inflate the balance.
• QA hold: Lot L1 of approved B is held pending inspection, while lot L2 passes. Verify the planning display separately from physical issue and consumption.
• Customer restriction: Order C1 is permitted; C2 awaits customer approval. Shared warehouse stock does not turn a customer-specific permission into a global one.
• Network failure: MES goes offline before an ERP revocation reaches it. Show the cached rule version and expiry, stop use after the defined limit, and resynchronize without duplicate events.
• Reverse trace: Assume B lot L1 was consumed in finished lots F1 and F2. Navigate from F1 to B, L1 and approval ID, then from L1 to F1/F2 and shipment destinations.
• Revocation: List untouched orders, issued stock, WIP, finished inventory and shipped output. Keep actual-use history while blocking new use.

For each case record prerequisite data, action, expected result, evidence, owner, environment and pass/fail outcome. Observe whether a rejected material is actually prevented from moving into the process, not merely whether an error message appears. Physical samples, similar maker numbers, alternate packaging, unit conversion and terminal language are valuable SAT checks. Repeat critical cases after a simulated failure and recovery.

A scoped 90-day rollout and useful measures

Ninety days here is an illustrative planning frame, not a delivery promise. Start with one product family where substitutions occur, map original/candidate relationships and past exceptions, then agree on owners, states, data authority and interface rules. Prototype the smallest approval and actual-use recording flow. Run rejection cases in FAT. Limit SAT to one Thailand line and verify two-way lot search and recovery before rolling out. Explicitly list the products and cases still outside scope.

Candidate measures include request-to-engineering-decision time, QA and customer waiting time, activation propagation delay, attempted noncompliant issues detected, completeness of consumed-lot records and time to identify affected finished lots. Rejection counts may increase immediately after controls are installed because previously invisible attempts become visible. Define the denominator, scope, timestamp and exclusions before comparing periods. Measure operator effort too, so control does not become excessive manual entry.

Illustrative prioritization

If a plant has, for example, 20 candidate relationships but cannot migrate all of them together, rank them by shortage exposure, product/customer impact, evidence readiness and tracing difficulty. The number 20 is a hypothetical example, not a survey finding. A frequently used substitute with clear authorization conditions can validate the core rules; customer restrictions and one-off deviations can follow. Do not leave high-risk materials uncontrolled while waiting for the new system—keep existing manual hold and dual-check procedures until acceptance.

FAQ: alternate part approval control

Is adding a substitute to the BOM enough?

No. A BOM may represent configuration and planning conditions, but it does not necessarily contain engineering and customer evidence, supplier scope, quality holds and the lot actually consumed. Design candidate status, activation and shop-floor verification explicitly, even if the ERP has a standard substitute feature.

Will MRP automatically choose an approved alternate when the preferred item is short?

It depends on the product version and configuration. Dynamics documentation describes a plan-group priority mechanism with prerequisites, but that does not establish customer and lot permission for every implementation. Test planning choice and physical consumption independently.

Who should approve alternate parts?

Engineering owns fit, QA owns testing and customer requirements, purchasing owns source conditions, planning/master data owns activation, and warehouse and production verify the actual material. Required customer approval comes from the relevant drawing or contract. Specify evidence, delegated authority, rejection and revocation rather than relying only on department names.

When may old stock still be used?

That decision combines effective dates with open purchase orders, released production orders, WIP, inventory, customer orders and quality conditions. Distinguish a stop on new use from the disposition of already-started work and link both to the relevant revisions.

Is EPCIS required for substitute-lot traceability?

Not universally. GS1 EPCIS is useful for interoperable event sharing, but it does not replace internal approval or BOM management. First make actual-lot genealogy searchable in both directions, then choose a partner-sharing format based on requirements.

What should an RFP and FAT/SAT test first?

Begin with refusal of an unapproved, wrong-customer, expired, QA-held or over-limit lot and behavior during a network failure. Then prove that accepted consumption links the work order, BOM revision, approval ID, component lot and affected finished lots.

Conclusion

Alternate part approval control runs from candidate evidence through engineering, QA, procurement and customer authorization to BOM/MRP activation, shop-floor rechecking and two-way actual-lot traceability. Specify conditions and data authority in the RFP; make refusal and reverse-trace scenarios central to FAT/SAT. Vendor-native substitution functions can help, but their scope must be checked against the plant’s approval and genealogy requirements.

TOMAS TECH can help Thailand factories map the current approval ledger, BOM, MRP and shop-floor records, then shape an RFP and FAT/SAT cases before a software decision. If the first question is where “usable for this order” should be decided, you can discuss it through our contact page.

References

• Microsoft Learn: Item substitution for formulas and bills of materials
• Microsoft Learn: Bills of materials and formulas
• Microsoft Learn: Manage changes to engineering products
• Microsoft Learn: Quality orders
• Microsoft Learn: Electronic batch records
• GS1: EPCIS and CBV
• GS1: Global Traceability Standard