Plan Old and New Stock Around an Approved Substitution

An approved replacement does not automatically make old and new stock interchangeable for every open obligation. Start with the exact substitution decision, divide demand by its allowed item and allocate each supply pool only to the uses it is authorized to serve.

The deliverable is an approved substitution cutover and demand-allocation record. It translates a completed technical decision into a bounded procurement plan. It does not assess equivalence, modify a product, execute a physical kit changeover or approve a new application. No actual substitution approval, stock record or affected order list has been supplied.

Read the approval as a scope boundary

Identify the old and new item references, revisions, units and the issuer of the approval. Preserve its effective conditions, included uses, excluded population and any dependencies. An approval to introduce the new item for future projects may leave existing customer obligations unchanged.

Determine whether the decision requires the new item, permits either item, or applies only after a stated event. Those distinctions change allocation. “Approved for new” does not automatically mean “must use new,” and permission to use new does not establish permission to use remaining old stock after the cutover. Where the record is silent, return the question to its owner.

Keep the technical approval separate from commercial permission to place orders. A valid substitution decision may still require a revised purchasing quantity, supplier terms or customer-specific authorization. Conversely, a purchasing approval for a cheaper item cannot resolve an unapproved technical difference.

Partition the open obligations before pooling supply

Choose a snapshot date and planning horizon with explicit start and end points. Include individual need dates and the approval’s effective boundary. Use the actual event specified in the approval rather than selecting order date, receipt date or use date for convenience.

Assign each outstanding obligation to one of four working groups: old item required; new item required or selected under the approval; either item expressly permitted; or applicability unresolved. These are administrative categories, not new permissions. Reference the exact decision supporting each assignment.

Each unit of demand belongs to one group at a time. If a single order contains different approved uses, split its quantity into traceable sublines rather than duplicating the full order under both old and new items. Check that the groups reconcile to the original outstanding total.

The unresolved group needs an owner and a purchasing consequence. Do not allocate the apparently abundant item to it simply to balance the sheet. Ask whether the affected commitment should remain paused pending clarification, while keeping separately supported demand decisions available to their owners.

Keep old and new inventory identities intact

Record eligible old stock and eligible new stock separately, with the established status and permitted-use scope for each. A sum of both inventories may describe a physical quantity, but it cannot show whether each demand group is covered. Do not relabel the old item as the new item in the ledger to simplify the total.

Use the same reservation convention on both sides. If demand totals include already reserved obligations, include the stock assigned to them in the corresponding eligible supply pool and allocate it once. If the demand and supply have already been reduced by matched reservations, use those remaining figures. A reservation must not be subtracted twice or used to satisfy both groups.

Apply the same distinction to open purchase commitments. Identify which item each actual order supplies, its remaining quantity and relevant dates. An existing old-item order does not automatically become a new-item order because the approval was issued. Any amendment needs the required commercial action and evidence.

Build a procurement cutover record

Keep the allocation choice visible where both items are permitted. A buyer may have reasons to select one pool first, but the worksheet does not invent that priority. The authorized owner should identify the chosen sequence and its consequences for the other obligations.

Hypothetical example: 60 obligations across two revisions

Assume one fictional passive component with revisions Old and New, both counted in individual units. The example window covers days 1–45, and the scope and required dates are expressly assumed resolved. The 60 outstanding demand units consist of 20 that still require Old and 40 assigned to New under an existing fictional approval and allocation decision.

In this example, the approval does not establish permission to use Old for the 40 New-assigned units. That is a deliberate scope boundary, not a technical finding that the old part is incompatible. There are no either-item or unresolved demand quantities in the arithmetic, although both groups would be shown if they existed.

There are 25 eligible Old units, before reservation netting, and no New stock or applicable inbound supply. The 20 Old-required obligations are included in the demand total; any stock reservation for them is part of the 25 and is not subtracted separately. Allocate 20 Old units to those obligations, leaving 5 Old units unallocated.

The New group still requires 40 units for a procurement decision. It is incorrect to subtract the 5 remaining Old units and request only 35 New units without a separate authorization permitting that allocation. Across the plan, 20 covered Old demand plus 40 uncovered New demand equals the original 60 obligations; 20 allocated Old stock plus 5 unallocated Old stock equals the 25 available Old units.

A proposal to buy 40 New units therefore addresses the New group’s uncovered quantity in this fictional case. It is not an actual release, supplier commitment or confirmation that delivery will meet the need dates. The 5 remaining Old units need their own owner decision; the calculation authorizes neither disposal nor reuse.

If a later authorized decision expressly permits those 5 Old units for five identified obligations previously assigned to New, issue a new allocation version. Only under that additional decision would New demand become 35 and the Old remainder become zero. Preserve the prior version so the changed purchasing quantity has an attributable cause.

Change repeat-buy instructions explicitly

Identify every active purchasing instruction within the approved scope: the next draft request, repeated template, open release proposal or standing replenishment direction actually in use. Do not assume a specific system or that changing one item description updates all dependent instructions.

For each, record the authorized treatment: retain Old for identified obligations, stop an uncommitted Old proposal, request an amendment, or prepare a New request. Keep “change requested” separate from “change confirmed.” An accepted old-item purchase may remain a commitment while an amendment is being negotiated.

Do not cancel all Old purchasing if a supported Old-only shortfall remains. Equally, do not let a copied historical order recreate Old stock after the owner has approved a narrower cutover. The aim is a traceable instruction for each demand group, not simply the newest item everywhere.

Reconcile the remainder and close at the right level

Review the stock and demand partition again after a material approval change, receipt, cancellation or allocation decision. A new receipt should reduce its linked remaining inbound quantity rather than create another independent source. Preserve item identity throughout the transition.

Assign unallocated Old stock to an owner with a permitted next question. Possible future-use or disposition proposals remain proposals until approved. Physical segregation, relabeling, rework and kit changeover require their own authorized instructions; this procurement record gives none.

Close with the demand totals by allowed item, the covered and uncovered quantities, the purchasing instructions actually changed and every unresolved remainder. The record succeeds when the approved substitution’s limits survive into the next buy, without a hidden claim that the old and new items are universally equivalent.

Frequently asked questions

Does approval of a new item mean I can use up all old stock first?

Only when the approval and relevant obligation owners expressly permit that allocation. It may require New for some uses, retain Old for others or leave old-stock use unresolved. Preserve those distinctions and ask for clarification rather than treating approval of New as universal two-way interchangeability.

Why can’t five leftover Old units reduce the example’s New purchase to 35?

The example assigns 40 obligations to New and provides no permission to fulfill them with Old. The five Old units therefore remain outside that coverage. A later explicit allocation authorization could change the calculation, but a purchasing spreadsheet cannot create that permission on its own.

What should happen to an existing order for the old item?

Keep its actual commitment and remaining quantity visible. Compare it with Old-required obligations, then ask the authorized commercial owner whether an amendment is needed and possible under the terms. A substitution approval does not itself cancel the order or prove the supplier accepted a changed item.

Is the cutover record also a physical changeover instruction?

No. It allocates procurement demand under an existing approval and records the required purchasing changes. Handling leftovers, reworking kits, relabeling products and executing a configuration change require their own scope and authority. The record does not establish technical equivalence, safety approval or permission to dispose of stock.