Why Dates in MRP Matter: Understanding the “Sum Req’d Qty” in Cetec ERP

One of the most common questions from purchasing teams is: “Why does the ‘Sum Req’d Qty’ on my MRP Buy report sometimes look higher than I expect?”

It’s a fair question, especially when it seems like the MRP engine is ignoring “On Hand” inventory. But in reality, Cetec ERP’s MRP isn’t miscalculating; it’s doing something incredibly valuable. By factoring in dates, it flags potential gaps in material availability that could impact production.

For buyers, that’s a great thing. It gives you early visibility into risks, instead of letting missed allocations or outdated schedules cause late surprises.

What the “Sum Req’d Qty” Really Represents

The **Sum Req’d Qty** field on the MRP-Buy report is the system’s suggestion for how much material needs to be purchased. But it’s not just a quick subtraction like:

Qty Required - Qty On Hand - Qty On Order

Instead, Cetec ERP layers in **time-based planning**. That’s where the extra value comes in.

Why Dates Matter for Purchasing

If a job has already started and its required material wasn’t formally allocated, the system treats that demand as “at risk.”

Even if stock is sitting on the shelf, if it wasn’t assigned in time, MRP won’t assume it’s safe to count it.

That’s why sometimes the **Sum Req’d Qty** may equal the full requirement, even when QOH exists.

This doesn’t mean you must place a PO immediately. Instead, MRP surfaces an **Action Type** such as *Change PO Date* or *Expedite Work Order*. That’s a signal that the issue may be solved by rescheduling or reallocating - not just by buying more parts.

For buyers, this is a safeguard; the system is protecting your production schedule by showing where timing - not just inventory balance- creates risk.

How to Investigate: The Waterfall View

When the suggested quantity doesn’t look right, the **MRP Waterfall view** is the best tool. It lays out:

• Each demand (work orders, sales orders)
• Each source of supply (on hand, on PO, etc.)
• How quantities are matched against demand chronologically

This makes it clear whether On Hand or On Order inventory offsets demand - or whether timing left a gap.

**Example:** A Sum Req’d Qty of 5,825 might correspond to a single order. If your QOH wasn’t allocated before the work order started, MRP surfaces the full 5,825 as “at risk.” Without this visibility, production could start late.

Buyer Control: Editable Recommendations

**Sum Req’d Qty is editable, not a hard directive.** Cetec ERP assumes purchasing will review, adjust, and decide the right course of action. That may be:

• Placing a purchase order
• Expediting an existing PO
• Reassigning stock to the order

The system gives you the data; your team makes the call.

When to Use Lite Mode

If you prefer to ignore dates and look strictly at overall supply vs. demand, **Lite Mode** is available. Lite Mode runs the simpler calculation:

Total Demand - (On Hand + On Order)

This is useful for high-level planning or quick shortage checks. But for protecting live production schedules, the **date-aware standard MRP mode** is the safer guide.

Practical Takeaways for Buyers

• Check the **Waterfall**: See how MRP matched supply and demand over time.
• Look at **Action Type**: Often, a scheduling adjustment—not a new PO—resolves the issue.
• Use **Lite Mode** selectively: Helpful for raw totals, but less precise for production timing.
• Treat **Sum Req’d Qty** as a **flag, not a final decision**.

If the MRP report shows a higher-than-expected **Sum Req’d Qty**, it’s doing its job: protecting your schedule by highlighting at-risk demand. For buyers, this means fewer surprises on the shop floor and better-informed purchasing decisions.

Want a deeper walkthrough? See our [MRP Waterfall How-To Guide](https://cetecerp.com/support/how-to/how-to-run-mrp.html) and [Waterfall Types Blog](https://cetecerp.com/blog/standard-waterfall-allocation-waterfall.html).

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