ERP vs MRP for Distribution Businesses

ERP records what the company already agreed to do: buy, receive, sell, ship, invoice, pay. MRP plans what a factory should make and what materials that plan consumes. Most distributors need the first and only a sliver of the second. The expensive mistake is buying a manufacturing planner because you kit assortments or slap a private label on a carton, then spending a year feeding bills of material that a buyer could have managed as a kit item.

Oracle's MRP user's guide is useful because it does not pretend MRP is a warehouse tool (Oracle MRP overview). Material requirements planning assumes independent demand, lead times, BOMs, and a supply order that is a work order. Distribution assumes independent demand, lead times, and a supply order that is a purchase order. If your supply order is a PO, you want ERP purchasing and inventory, not MRP. If your supply order is a work order with components and a routing, you want MRP or a manufacturing module.

NetSuite, Acumatica, SAP Business One, and Dynamics 365 Business Central all sell manufacturing or MRP-shaped modules next to distribution. Fishbowl and Cin7 Omni sit in the light-assembly gap. Epicor Prophet 21 and Infor Distribution SX.e stay distribution-first; they are the wrong aisle if you are becoming a real manufacturer. The architecture choice is about the order you launch every day, not about a consultant's favorite module map.

A kit that is picked from finished components and boxed on the dock is a bill of materials on a sales order. Acumatica, NetSuite, SAP Business One, Business Central, Cin7 Omni, and Fishbowl all do this without an MRP run. You need component ATP, a kit explosion at pick, and a cost rollup the controller accepts. You do not need finite capacity planning.

Light assembly that always happens before the order — private-label shrink wrap, a standard value-add, a Monday kit wave — can still live in ERP as a work order or assembly document. The test: do you schedule machines and people by routing, or do you launch a batch when the buyer says the labels arrived? Batch launch is ERP. Routing and capacity is MRP.

Customer-specific kits are a price and BOM problem, not a factory problem. The national account who wants a unique assortment at a signed matrix needs the kit on the price book and the components reserved. Prophet 21 and Infor SX.e users do this as distribution. If someone tells you that requirement is why you need MRP, ask them to draw the work center. If they cannot, they are selling a module.

Startup distributors who 'might manufacture later' should buy inventory and accounting, not MRP. Cin7 Omni or Fishbowl can explode a kit. QuickBooks Enterprise will not plan a factory and should not be asked to. Keep the door open by choosing an ERP later that has an optional manufacturing module (Acumatica, NetSuite, Business Central) rather than a standalone MRP you will run in parallel.

At about $5M, the temptation is a consultant who grew up in manufacturing. Make them sit in receiving for a morning. If the work is POs, transfers, and kits, stay on a distribution edition. Acumatica's distribution management positioning is literally this split (Acumatica Distribution). Turn on manufacturing only when a named work center has a queue.

Multi-warehouse kitting (assemble in building A, ship from B) is still an ERP transfer-plus-assembly problem. MRP does not become necessary because geography appeared. Cold-chain assembly — kitting lots with expiry, FEFO on components, an 856 that lists lots — is a traceability problem. You need lot pedigree in the ERP and directed pick in the WMS. You still may not need MRP. If those lots are also FDA-regulated electronic records, Part 11 applies to the system that stores them (FDA Part 11), which is usually quality plus ERP, not an MRP run.

In a pure distribution ERP, the buyer owns the suggested PO. Reorder points, DRP, and vendor lead times live on the item. NetSuite's advanced inventory and Acumatica DRP are this layer. Unleashed and Cin7 do a lighter version. That is planning. It is not MRP.

When you add MRP, a planner owns a planned order that becomes a work order or a PO. Dual ownership without a rule is how you double-buy steel or under-buy a kit component. Write the rule before you enable the module: MRP may create planned POs for manufactured parents; buyers may not also min-max those same items. WMS never creates supply. CRM never creates supply. EDI 850s are demand, not supply.

EDI 855 dates must come from the same ATP the planner or buyer sees. If MRP promises a work order completion the warehouse cannot pack, the 856 will lie. Keep one available-to-promise. GS1's order-to-cash messages assume that honesty (GS1 EDI). Customer-specific pricing stays on the finished good in the ERP. Do not let MRP invent a cost that silently changes a contract margin you already signed.

Hudson Industrial Supply adds a chemical family and a private-label assortment: ten fasteners in a branded bin for a national account. A software seller called that manufacturing and quoted NetSuite MRP plus a shop-floor add-on. The founder almost signed because the word 'scale' was on the slide.

They walked the dock. The assortment is picked and dropped in a bin when the order prints. No machine. No routing. No labor standard that anyone would maintain. They kept Acumatica distribution, used kit BOMs, reserved components for that account's matrix price, and left manufacturing off. Fishbowl's kitting would have worked too if they had stayed on QuickBooks — they did not, because EDI and price books had already outgrown that path.

Worked numbers: 16 ERP seats, zero MRP seats, kit BOM for one national account, lot tracking on chemicals only. Go-live still month 7. They saved an estimated $30,000–$45,000 in year-one modules and workshops, and they avoided a planner role they would have staffed with the already-busy buyer. The trigger they wrote: if they add a filling line with a real routing and a second shift, reopen Acumatica Manufacturing or NetSuite. Until a routing exists, MRP is a costume.

If you already own NetSuite, read inventory and demand planning before you buy a third-party MRP. If you own Acumatica, read distribution requirements planning and only then manufacturing. If you own Business Central, the manufacturing app is a separate decision from the warehouse app. If you own SAP Business One, production is an add-on conversation with the partner. If you own Prophet 21 or Infor SX.e, stay in distribution unless your board has approved becoming a manufacturer.

Implementation time for kit BOMs is days or weeks inside an already-live ERP. Implementation time for MRP is a second project: clean BOMs, clean lead times, a planner, and a willingness to stop cowboy purchasing. TCO is not the module price. TCO is the planner and the inventory swing while the algorithm trains on your messy history.

Manhattan, Körber, and Extensiv will not settle an ERP-versus-MRP argument. WMS executes. It does not decide whether you are a factory. HubSpot and Salesforce will cheerfully store a 'manufacturing' stage that has no work order behind it. Ignore that stage. The document that ships is the truth.

Distribution requirements planning answers a warehouse question: given demand at each location, what should we transfer or buy, and when. MRP answers a factory question: given a master schedule, what components and work orders do we launch. Acumatica's distribution edition includes DRP next to inventory for a reason. NetSuite's advanced inventory replenishment is in the same family. Neither is a shop-floor scheduler. Confusing the two is how a $5M wholesaler ends up in a manufacturing workshop they will not finish.

Use DRP when you have two warehouses, uneven demand, and a buyer who still builds POs from a gut feel. Use min-max when you have one site and stable vendors. Use MRP when a work center has a queue you can name. Hudson had two buildings and a kit. They needed transfer suggestions and a kit BOM. They did not need a planned order that exploded a routing. The seller who called kit 'MRP' was renaming pick-and-pack.

Implementation time for DRP inside a live ERP is a few partner weeks plus clean lead times. Implementation time for MRP is a BOM project, a planner, and a political fight with purchasing. TCO follows the people. A DRP license is cheap compared with hiring someone to babysit planned orders that buyers will override. If every planned PO is overridden, you do not have planning. You have a report that nobody believes, whether the logo says NetSuite, Acumatica, or a standalone MRP you bolted onto QuickBooks Enterprise. Write an override log for 30 days after you turn planning on; if more than a third of suggestions die, fix lead times and min-max before you buy another module.

Customer-specific pricing still sits above any planner. A DRP suggestion that replenishes a reserved national-account SKU for general sale will steal a contract. Keep reservations visible to planning. EDI 850 demand should raise the plan the same day, not after a weekly batch. Those two rules prevent the 'planner versus CSR' fight that makes MRP look smarter than it is on a wholesale floor. Hudson's buyer spent fifteen minutes each morning on exceptions only; that is the operating picture you want, not a nightly MRP packet nobody opens. They never created a planner seat. They did create a Friday review of kit component stock for the one national-account assortment, which is a meeting, not a manufacturing module. That Friday list is still a spreadsheet. They are fine with that. A spreadsheet that one buyer owns is cheaper than an MRP seat nobody will feed.