Material master before S/4HANA conversion: what to clean and when

In an SAP S/4HANA system conversion, the company keeps its business data, and that includes the material master with all its problems. So clean up first everything that blocks the load or distorts planning: materials flagged for deletion, inactive items with no stock and no open documents, duplicates with stock or open orders, inconsistent plant-level MRP data and wrong units of measure. Cosmetic or low-impact work, such as standardizing descriptions across the long tail, can wait until after go-live, as long as it sits in a governance plan with an owner and a deadline.

"We'll clean it up after go-live."

I have heard that sentence in many SAP projects. It shows up at kickoff, everyone nods, and the cleanup becomes a line in the project plan that nobody opens. The next scene usually goes like this: first conversion mock, someone runs planning in the new environment and starts seeing purchase proposals for items nobody has used in years. The planning data for those materials was still there, filled in, waiting for someone to remember it.

S/4HANA forgets nothing. It takes the whole material master along, the good records and the bad ones.

What does SAP say about data in a system conversion?

In its SAP Activate methodology material, SAP explains that in a system conversion the company keeps "their business data, custom development, and configuration" (SAP Learning, Analyzing System Conversion). The same lesson lists, in the preparation step: "Clean up custom code and reduce data volumes."

The lesson also points to two tools that feed your cleanup list:

• SAP Readiness Check: it provides the subset of simplification items that may apply to the analyzed system and an analysis of data volumes in the source system.
• Simplification items: the guidance is to determine which ones are relevant for that specific system.

My operational reading: a conversion is a move. If the truck leaves loaded with materials nobody uses, it arrives loaded with materials nobody uses. The difference is that now you paid for the freight.

Why does the material master weigh so much on planning after conversion?

Because material requirements planning reads the material master. In its S/4HANA process documentation, SAP states that "MRP-relevant data is stored in the material master record at plant level" and that MRP depends on configuration and on maintaining that data in the material master: MRP type, planned delivery time or in-house production time, lot-sizing key. The procurement quantity results from the lot-sizing procedure stored in the material master record (SAP Learning, Running Materials Requirements Planning).

The same source makes two points that change the cleanup conversation:

• In SAP S/4HANA, "the MRP area is active by default and cannot be deactivated."
• If you want to plan storage locations separately within a plant, you must configure MRP areas.

For the people who maintain the material master, this means inconsistent plant-level MRP data does not stay hidden. It turns into purchase, production or transfer proposals. And if your ECC system plans any storage location separately today, map it before the conversion, because in the target system that runs through MRP areas.

What should you clean up before the conversion?

My rule is simple: clean up first whatever blocks the load, distorts planning or breaks interfaces and custom code. Everything else goes into the post go-live queue.

1. Materials flagged for deletion and inactive items with no stock and no open documents

These are the obvious candidates for reducing data volume, which is exactly what SAP asks for during preparation. One caution: flagged for deletion is not the same as deleted. Before archiving or deleting any record, confirm with your SAP team and with audit and tax which retention rules apply to your company. That is my recommendation, not a regulation. The diagnostic and treatment steps for the database are described on our data cleansing page.

To define "inactive", use a threshold set by the business, for example a number of months without movement, and name the exceptions explicitly: seasonal items, critical maintenance spare parts, safety stock materials. A spare part that has not moved in years may be exactly the one that keeps a line running.

2. Duplicates with stock, open orders or bills of materials

A duplicate with no activity is just volume. A duplicate with stock, an open order or a place in a bill of materials is a risk, because planning sees two items where there is one. These need a decision beforehand: which code survives, and where stock and documents go. The criteria for finding duplicates are in our article on how to identify duplicate materials.

3. Inconsistent plant-level MRP data

An MRP type set on an inactive item, a zero planned delivery time on a purchased item, a lot size that does not match the supplier's packaging. Since MRP in S/4HANA reads these fields at plant level, review them before the first mock.

4. Units of measure and conversions

A wrong base unit or an inconsistent conversion factor between order unit and base unit produces wrong quantities in orders and inventory. This is the kind of error that shows up in the mock and eats a full week of fixes.

5. Fields used by interfaces and custom code

If an interface with your WMS, MES or procurement portal reads a material field, or if custom development depends on a specific material group, that field must be right beforehand. The technical team knows which ones, so the list comes from the interface inventory and from the custom code that is already being reviewed during preparation.

What can wait until after go-live?

Whatever does not block the load, does not change planning and does not break an interface can wait. Examples:

• Full description standardization across the long tail: slow-moving items with free-text descriptions can be standardized later, family by family, using a material description standard (PDM) with a characteristics template.
• Enrichment of non-critical attributes: technical data nobody checks to buy, plan or invoice.
• Reclassification of slow-moving items: group or class adjustments with no impact on interfaces, regulatory reports or determination rules.

The condition for waiting is having an owner, a deadline and governance rules for the new material master. Without them, "later" becomes never, and every new item created in S/4HANA is born with the same problems as the old ones.

Who decides each cleanup item?

In my experience, cleanup stalls when IT decides alone what is inactive. IT knows the volume, but maintenance knows whether an item is a critical spare part, and procurement knows whether a supplier still delivers that code.

Cleanup item	Before or after	Why	Who decides
Materials flagged for deletion	Before	Reduces volume; SAP lists reducing data volumes in the preparation step	Master data team, validated with the SAP team, audit and tax
Inactive items with no stock and no open documents	Before	Reduces volume and avoids planning dead items	Data owner per area (procurement, maintenance, production planning)
Duplicates with stock, orders or bills of materials	Before	Planning sees two items where there is one	Production planning and procurement, with the master data team
Plant-level MRP data	Before	MRP reads these fields at plant level	Production planning and MM/PP consultant
Units of measure and conversions	Before	Wrong quantities in orders and inventory	Procurement, logistics and master data team
Fields used by interfaces and custom code	Before	Breaks integrations and custom development	SAP technical team
Long-tail description standardization	After, with a plan	Does not block the load or planning	Master data team
Non-critical attribute enrichment	After, with a plan	Does not change processes at go-live	Master data team and business users

Fields with tax impact, such as the NCM in Brazil (the Mercosur Common Nomenclature, which Brazil's federal revenue service, the Receita Federal, defines as a regional nomenclature for categorizing goods), go on the list with the tax team as owner. The master data team does not set tax rules.

How do you prove the cleanup did not break anything?

Cleanup without evidence turns into a debate of opinions at the steering committee. Use the conversion mocks to measure:

Compare counts and balances

Number of materials by type and by plant before and after, and the stock balance of the items that remain. The difference must match the approved list of deletions and merged duplicates.

Run a test MRP

Compare purchase and production proposals with what planners expect. A proposal for an item that should be inactive signals MRP data that slipped through.

Check bills of materials and open orders

No active bill of materials should point to a deleted material, and no open order should be left orphaned after duplicates are merged.

For the before-and-after quality baseline, the indicators are in our article on how to measure master data quality.

Hypothetical example: triaging one plant

Hypothetical example, with illustrative numbers. A manufacturer is converting ECC to S/4HANA. Its main plant has 40,000 materials. The steering committee defines an inactive item as one with no movement for 36 months, no stock and no open documents, except for critical spare parts flagged by maintenance and seasonal items flagged by sales.

The triage creates three groups: items flagged for deletion, which go to archiving validation with the SAP team and audit; inactive items outside the exceptions, which get the same treatment; and duplicates with stock, which get a decision on which code survives. Planning reviews the MRP data of active items before the first mock. Description standardization for slow-moving families goes into the governance plan for the six months after go-live.

In the mock, the team compares counts and balances, runs the test MRP and checks bills of materials. Only then does the committee sign off the final list.

Where to start cleaning the material master before S/4HANA

1. Run the SAP Readiness Check and list the simplification items relevant to your system. They are the first input to your cleanup list.
2. Extract the material master with stock, last movements, open documents and bill of materials usage, plant by plant.
3. Agree on the inactivity criteria and exceptions with the business, in writing.
4. Split "before" and "after" using the table above, and assign an owner to every line.
5. Validate archiving and deletion with the SAP team and with audit and tax.
6. Use the mocks to prove the result: counts, balances, test MRP, bills of materials and open orders.
7. Build the governance plan for whatever was left for later, with a deadline and an owner.

Customers and suppliers follow a different logic in the conversion, covered in our article on Business Partner in S/4HANA. For the broader migration view, see data migration for SAP projects. The full service scope is on our SAP S/4HANA data migration page.

Frequently asked questions

Do I need to clean the entire material master before converting?

No. Clean up first what blocks the load, distorts planning or breaks interfaces: deletion-flagged items, inactive items with no stock and no open documents, duplicates with activity, plant-level MRP data, units of measure and fields used by integrations. The rest can go into a post go-live governance plan with an owner and a deadline.

Can I delete old materials before the conversion?

SAP lists reducing data volumes in the preparation step, but archiving or deleting records is a decision to validate with your SAP team and with audit and tax, because of retention rules. My recommendation is to treat deletion as an approved process, never as a cleanup script run on a Friday afternoon.

What should I do with materials flagged for deletion?

Check whether they still have stock, open documents or bill of materials usage. If not, they are candidates for volume reduction before the conversion, subject to archiving validation. If they do, either the flag is wrong or a process still depends on the item, and that must be resolved first.

Should the cleanup happen in ECC or in S/4HANA?

For items that block the conversion or distort planning, in ECC, before the conversion, because a system conversion keeps business data, and whatever is wrong at the source carries over to the target. Whatever can wait is handled in S/4HANA after go-live, under the governance rules of the new material master.

Does a system conversion versus a new implementation change what to clean?

It changes the timing. In a system conversion, SAP describes that the company keeps its business data, so the cleanup has to happen at the source. In practice, in a new implementation, data is migrated into a new system, and selection and cleansing happen within the migration itself, with mapping and load tests. In both cases, the "before" and "after" triage still applies.

How far in advance should the cleanup start?

There is no standard lead time that fits every company. My recommendation is to start as soon as the Readiness Check results are available and before the first mock, because the mock is what proves whether the cleanup worked. Starting after the first mock means fixing and testing at the same time.

How 4MDG can help

4MDG migrates data into SAP, including from ECC to S/4HANA, with a methodology integrated with SAP Activate: source-to-target mapping, load tests with corrections before the final load, and a controlled cutover with acceptance criteria per object. Before loading, we cleanse the main master data, including materials, through deduplication, description standardization, enrichment and validation. See our SAP S/4HANA migration page. If you want to know where your material master stands before setting the cleanup scope, request our assessment: it runs on a real sample of your data, with nothing installed in your environment. Or reach us through our contact page.

Sources

• SAP Learning. Discovering SAP Activate: Implementation Tools and Methodology, lesson "Analyzing System Conversion". https://learning.sap.com/courses/discovering-sap-activate-implementation-tools-and-methodology/analyzing-system-conversion_e1dd4c82-3bcf-4cd0-a4f8-6a2ce6ce8a64. Accessed on October 13, 2026.
• SAP Learning. Business Processes in SAP S/4HANA Sourcing & Procurement, lesson "Running Materials Requirements Planning". https://learning.sap.com/courses/business-processes-in-sap-s-4hana-sourcing-procurement/running-materials-requirements-planning. Accessed on October 13, 2026.
• Receita Federal (Brazil's federal revenue service). NCM (in Portuguese). https://www.gov.br/receitafederal/pt-br/assuntos/aduana-e-comercio-exterior/classificacao-fiscal-de-mercadorias/ncm. Accessed on October 13, 2026.

The SAP features mentioned here vary by release and should be validated against the documentation for the version your company runs.

Paulo Cordeiro, founder and CEO of 4MDG.