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There is a meeting that happens in almost every manufacturing business on the planet.
It has different names. S&OP. SIOP. IBP. The Monthly Review. The Commercial Alignment Call.
It happens once a month.
It takes most of a day.
It involves the most expensive people in the building.
And in most businesses, it doesn’t work.
Not because the people in the room are incompetent. Not because the data is unavailable. Not because leadership doesn’t care.
It doesn’t work because the process is structurally compromised — and nobody says so out loud.
This post is about why SIOP fails, what it costs when it does, and what a version that actually works looks like. It is written for leaders who have sat in enough of those meetings to recognise something is fundamentally wrong but haven’t yet been able to name it precisely.
- What SIOP Is Supposed to Do
Let’s start with intent, because it matters.
Sales, Inventory and Operations Planning — in its purest form — is a decision-making process designed to align demand, supply and finance into a single coherent plan.
The goal is elegant:
One version of the truth.
One set of priorities.
One plan that everyone is executing against.
When it works, the business knows what customers want, knows whether it can deliver it, knows at what cost, and has made conscious trade-off decisions where gaps exist.
When it works, inventory is a deliberate buffer, not an accident.
When it works, premium freight is an exception, not a budget line.
When it works, capacity decisions are made weeks ahead, not hours before.
When it works, finance doesn’t spend half the month reconciling why the forecast said one thing and the factory did another.
That is what SIOP is supposed to do.
Now ask yourself honestly — is that what your process delivers?
For most leadership teams, the honest answer is: sometimes. Partially. In certain areas. When conditions are stable.
Which is another way of saying: not reliably. Not structurally. Not by design. - The Anatomy of a Broken Process
Walk through what typically happens.
The demand team produce a forecast. It’s built from a combination of sales pipeline data, historical trend analysis, market intelligence and — if we’re being honest — a degree of optimism. The commercial team want targets to look achievable. The product managers advocate for their lines. Regional teams submit numbers that reflect aspiration as much as probability.
The forecast arrives at operations.
Operations review it with deep scepticism. They’ve been here before. Q1 demand was overstated. The launch that was “confirmed” got delayed six weeks. The product mix shifted without warning and left the factory making the wrong things at full speed.
So operations builds buffer. Quietly. Into lead times, into capacity plans, into inventory targets. A hedge against the forecast they don’t believe.
Finance look at both sets of numbers and produce a third version — one that reconciles to the budget they agreed in October, because that’s what the board approved and deviations need explaining.
By the time the SIOP meeting happens, there are three plans in the room pretending to be one.
Nobody says this out loud.
The meeting discusses the gap between forecast and budget. It debates whether a customer miss is a supply problem or a demand problem. It reviews the inventory that somehow keeps growing despite everyone agreeing it should fall. It approves actions that everyone in the room knows will not be completed before next month’s review.
Then it ends.
And the cycle repeats. - The Seven Structural Failures
The broken SIOP isn’t a personality problem. It’s a design problem. And the design fails in predictable ways.
Failure One: Forecast ownership without forecast accountability.
Someone produces the forecast. But nobody is accountable for its accuracy. When the forecast is wrong — and it will be wrong — the question is never “why was our process wrong?” It’s “what happened in the market?” The market becomes the alibi. Forecast error is normalised rather than interrogated.
A good SIOP process treats forecast accuracy as a KPI, not a disclaimer.
Failure Two: The process is a reporting event, not a decision event.
In too many businesses, the SIOP meeting is a structured review of what has already happened. Last month’s performance. This month’s gap. Next month’s risk. Charts are presented. Numbers are read out. Questions are asked that require follow-up. And the meeting ends without a material decision having been made.
Real SIOP is a decision-making forum. It exists to make trade-off calls — capacity versus cost, service versus inventory, short-term delivery versus long-term stability — that only the most senior people in the business can make. If your SIOP meeting is generating actions but not decisions, it’s a reporting cadence wearing SIOP’s clothes.
Failure Three: Siloed preparation with no shared baseline.
Sales prepare their numbers.
Operations prepare theirs.
Finance prepare theirs.
They arrive at the meeting with different assumptions, different time horizons, and different definitions of the same words. “Committed” means something different to a sales leader and a supply planner. “Available” means something different to a warehouse manager and a customer service team.
The meeting then spends 40% of its time reconciling data rather than making decisions.
Effective SIOP requires a single integrated model, prepared collaboratively, before anyone enters the room. The meeting should be discussing conclusions, not comparing spreadsheets.
Failure Four: The wrong level of granularity.
SIOP is a strategic process. It should operate at product family, customer segment, and site level. It should look across a rolling 12–18 month horizon.
Many businesses try to run SIOP at SKU level. They get lost in the detail. The meeting becomes an extended planning session for the next four weeks, and the strategic decisions — about capacity investment, portfolio rationalisation, make-versus-buy — never surface.
The granularity of the SIOP conversation should match the level of the people in the room. If your VPCO is debating individual SKU replenishment quantities, the process is broken.
Failure Five: Inventory treated as an outcome rather than a decision.
Inventory is one of the most expensive things a manufacturing business owns.
It consumes cash. It occupies space. It degrades, obsoletes, and has to be counted, moved, and insured. It hides process problems. It distorts planning signals. It creates complexity at precisely the moments — new product launches, portfolio rationalisation, M&A integration — when you need simplicity.
In most SIOP processes, inventory is reviewed but not designed. The stock report shows the number. The number is too high. Actions are agreed to reduce it. Next month the number is still too high.
That’s because nobody made a structural decision about what the inventory should be, and why, and what process changes are required to sustain it at a different level.
Target inventory is a strategic choice. It reflects your lead time ambition, your forecast accuracy, your supplier reliability, your batch size design, and your service level commitments. Change those inputs, and you can change the inventory sustainably. Review the number without changing the inputs, and you are applying pressure to a system that will spring back.
Failure Six: Finance as scorekeeper rather than partner.
Finance’s role in most SIOP processes is to validate the numbers and report the gap to budget.
That’s necessary. It’s not sufficient.
Finance should be a genuine analytical partner in the SIOP process. They should be able to model the capital implications of different demand scenarios. They should quantify the cost of carrying excess inventory versus the cost of a customer miss. They should translate operational decisions into working capital and EBITDA terms in real time, so the leadership team can make genuinely informed trade-offs.
When finance is a reporting function in the SIOP meeting rather than a modelling partner, the conversation stays tactical. The decisions stay short-term. And the financial consequences of operational choices don’t surface until the month-end close — when it’s too late to do anything about them.
Failure Seven: SIOP disconnected from execution.
The most common failure of all.
The SIOP plan is agreed. It looks reasonable. Everyone leaves the meeting aligned.
Then the week starts. A customer escalates. A supplier misses. A machine goes down. Engineering releases a change. And the plan is abandoned — not formally, not through a structured re-plan, but through a thousand small local decisions made at shift level, at production control level, at the sales counter.
By week three, the SIOP plan and operational reality have diverged so significantly that the next SIOP cycle starts with a gap analysis rather than a refinement.
Execution without feedback is not a planning failure. It’s a governance failure.
The SIOP process needs formal mid-cycle review mechanisms — weekly supply reviews, demand sensing checkpoints, exception escalation triggers — that connect the monthly strategic rhythm to daily operational reality. Without them, SIOP is a plan that gets filed and forgotten. - What It Costs
Let’s be specific about consequence, because the structural failures described above are not abstract.
Every broken SIOP meeting is an opportunity cost event.
Premium freight. When demand exceeds supply unexpectedly — or when the supply plan was never credible — the response is speed. Air freight. Expedited logistics. Express tooling. None of that was in the cost plan, and all of it erodes margin. In businesses with global supply chains and complex product mixes, premium freight can consume 2–4% of revenue. Not because logistics teams are careless. Because the planning process failed to surface the constraint three weeks earlier when it could have been managed.
Excess inventory. When the forecast is wrong in the optimistic direction — and it usually is — the factory makes product that doesn’t ship. That product becomes inventory. That inventory sits on the balance sheet consuming cash and obscuring planning signals. When the next planning cycle runs, inventory distorts the demand signal further, creating a feedback loop of inaccuracy. Businesses with structurally weak SIOP processes consistently carry 30–60 days more inventory than operationally justified.
Underutilised capacity and overtime. When the plan is unreliable, operations hedges. They undercommit to capacity in formal plans, then overreact when demand crystallises. The result is idle time followed by overtime — both expensive, both avoidable, neither visible in the SIOP process that was supposed to prevent them.
Customer service erosion. Late deliveries. Partial shipments. Missed promises. These don’t appear in the SIOP review as a planning failure. They appear as individual customer escalations, managed by account managers and customer service teams at significant effort cost. The root cause — a SIOP process that couldn’t create a credible commitment — is rarely named.
Leadership distraction. The most underappreciated cost. When SIOP doesn’t work, the gap-filling happens manually. Senior operations leaders spend disproportionate time in firefighting mode — resolving supply crises, managing customer escalations, negotiating cross-functional prioritisation in real time. That time comes directly from strategic activity. Transformation slows. Improvement programmes stall. Capability development is deferred. The hidden cost of a broken SIOP process is not just financial. It is organisational capacity.
Add those together across a mid-sized manufacturing business and you are looking at tens of millions of pounds of value destruction annually. Not from bad intent. From a process that was never designed to actually work. - Why Leadership Tolerates It
This is the uncomfortable question.
If the costs are real and the failures are structural, why does the broken SIOP persist?
Three reasons.
The process looks like it works. There is a meeting. It is well-attended. There are slides. There are actions. There is a rhythm. From the outside — and often from the boardroom — it looks like a functioning process. The dysfunction is visible only at the detail level, and senior leaders are rarely close enough to the detail to see it clearly.
The problems are lagging. The premium freight that appears in this month’s actuals is the consequence of a planning failure six weeks ago. The inventory that’s grown by £3m this quarter reflects decisions that were made — or not made — in SIOP reviews that looked entirely normal at the time. The lag between cause and consequence makes it hard to attribute the problem to the process. Instead it gets attributed to the market, the supplier, the customer, the product.
Fixing it is genuinely hard. A real SIOP transformation requires cross-functional behaviour change. It requires sales to accept forecast accountability. It requires operations to share capacity constraints transparently rather than manage them quietly. It requires finance to build modelling capability rather than just reporting capability. It requires leadership to make — and stick to — difficult trade-off decisions in real time. That’s a significant ask. It’s easier to keep attending the monthly meeting and agree that the process needs improving.
The result is a comfortable dysfunction. Everyone knows the meeting doesn’t quite work. Nobody is ready to do what it takes to fix it. - What a Lean-Aligned SIOP Actually Looks Like
Lean thinking applied to SIOP does not mean adding more visual management to a broken process.
It means designing the process to create flow — of information, of decisions, of accountability — in the same way Lean design creates flow in a production system.
Here is what that looks like in practice.
Principle One: One integrated plan, built collaboratively.
The Lean concept of a single piece flow applied to planning. Instead of three functions producing three parallel versions of the plan and reconciling them in the meeting room, a genuinely integrated process builds a single model together, in structured pre-work sessions, before the executive forum convenes.
Demand planners, supply planners, and financial analysts work in the same data environment, using agreed assumptions and agreed definitions. Gaps and risks are surfaced and scenario-modelled before the leadership team sees them. By the time the executive SIOP meeting happens, the conversation is about which scenario to select and why — not about which number is right.
Principle Two: Meaningful metrics at the right level.
Your SIOP process should track a small number of genuinely predictive KPIs.
Forecast accuracy by product family and time horizon. Inventory days by category. Schedule adherence. Customer on-time in full. Capacity utilisation versus plan. Premium freight as a percentage of revenue.
Not because these make a nice dashboard. Because these are the variables that determine whether your SIOP process is working as a system.
Trends in these metrics tell you whether your process is improving or degrading. Spikes in these metrics tell you where the integration is breaking down. Review them every cycle, track them over time, and use them to drive process improvement rather than just performance reporting.
Principle Three: Decisions not presentations.
The executive SIOP forum should have a defined purpose: to make the trade-off decisions that can only be made at leadership level, and to provide the direction that enables the organisation to execute for the next 30 days with clarity.
That means the agenda is structured around decisions, not updates. Each section of the meeting should end with a clear decision or a clearly articulated escalation — not an action to “review further.”
If your SIOP meeting regularly runs long because of extended debate, that is a symptom of inadequate pre-work. If it runs short because there are no difficult decisions to make, that is a symptom of insufficient strategic horizon. The right balance is a tightly prepared, deeply substantive executive conversation — probably two hours — that generates four or five significant cross-functional decisions per cycle.
Principle Four: Inventory is designed, not managed.
A Lean-aligned SIOP process treats inventory as a design output.
For each product family, you establish target inventory based on: demand variability (what is our forecast error and what buffer does that require?), supply reliability (what is our supplier OTIF and what does that require us to hold?), lead time strategy (what delivery commitment have we made to customers, and what inventory position does that imply?), and batch size design (what are our changeover constraints and how do they force us into batch production that generates inventory?).
When those inputs change — because lead times improve, because forecast accuracy improves, because changeover times reduce — the target inventory changes with them. It becomes a dynamic parameter that reflects the state of the operating system, not a static number negotiated at budget time.
This is a fundamentally different conversation from “inventory is too high, let’s reduce it.” It is: “here are the four structural drivers of our inventory level, here is how each one is performing, and here is the improvement roadmap that will sustainably reduce our working capital requirement by £Xm over the next 18 months.”
That conversation belongs in SIOP. It almost never happens there.
Principle Five: Execution is connected, not assumed.
The monthly SIOP cycle sets direction. But direction requires translation.
A Lean-aligned process builds formal weekly rhythms that connect the monthly plan to operational reality:
A weekly demand review — a short, focused session where demand planners review actual orders against forecast, identify material deviations, and determine whether a mid-cycle exception needs escalating.
A weekly supply review — where operations confirm schedule adherence, surface any capacity or supply risks emerging within the SIOP horizon, and flag decisions that require cross-functional input.
A formal exception protocol — a defined escalation route for events that invalidate the agreed SIOP plan, with clear triggers, clear decision-makers, and a clear timeline.
These are not additional meetings for their own sake. They are the connective tissue between strategic planning and operational execution. Without them, the monthly SIOP plan is a wish list.
Principle Six: Accountability at every level.
The most important cultural shift.
Forecast accuracy must be owned. Not just measured — owned. The commercial leader is accountable for the quality of the demand signal. The operations leader is accountable for the credibility of the supply commitment. Finance is accountable for the quality of the integrated financial model. Each function owns their contribution to the plan and is accountable for its performance.
When forecast accuracy degrades, that is a commercial process problem. When schedule adherence collapses, that is an operational discipline problem. When the financial model doesn’t reflect operational reality, that is a finance process problem.
Lean’s principle of built-in quality applies directly to planning. You cannot inspect quality into a plan at the monthly meeting. You have to build quality into the planning process — through better demand sensing, through more transparent capacity management, through rigorous assumption documentation. Accountability is what drives that quality. - The Role of Technology — and Its Limits
A word on systems, because this conversation inevitably arrives there.
Many organisations respond to a broken SIOP process by investing in better technology. An upgraded ERP module. An advanced planning and scheduling system. A demand sensing platform. An integrated business intelligence layer.
These investments can add genuine value. Modern planning tools offer capabilities that were genuinely out of reach a decade ago — machine learning demand sensing, scenario modelling, real-time supply visibility, automated exception flagging.
But technology does not fix a broken process. It amplifies it.
If your SIOP fails because commercial and operational teams don’t trust each other’s numbers, a new planning system will not build that trust. It will give both sides more sophisticated numbers to distrust each other with.
If your SIOP fails because leadership doesn’t make decisions in the meeting, a better dashboard will give you more detailed information to not decide upon.
If your SIOP fails because inventory targets aren’t based on structural logic, an AI-powered replenishment system will optimise against the wrong parameters faster than you previously managed to do it wrong manually.
Technology should follow process design. Fix the governance, the accountability, the integration logic, the decision architecture. Then automate what you’ve designed. In that order.
The businesses that get the most from planning technology are invariably the ones that already had good SIOP discipline before they invested in the tools. - The Leadership Behaviour Question
Processes don’t run themselves. People run them. And the behaviour of senior leaders shapes every process in the building — whether they intend it to or not.
If the CEO consistently overrides the SIOP output to satisfy a specific customer or commercial pressure, the organisation learns that the SIOP plan is negotiable. Planning quality degrades accordingly.
If the CFO uses the SIOP meeting to reforecast the budget rather than to support operational decision-making, the process becomes a financial justification exercise. Transparency degrades accordingly.
If the COO allows operations to present capacity commitments that everyone knows are sandbagged, the commercial team will discount them and build their own estimates. Integration degrades accordingly.
Good SIOP requires a specific set of leadership behaviours.
Transparency over protection. Leaders who surface problems early — even when the problems are uncomfortable — enable the SIOP process to function as designed. Leaders who protect their functions from scrutiny guarantee that the meeting will deal with symptoms rather than causes.
Decision over deferral. The SIOP meeting is the right moment to make the difficult trade-off. Deferring to a sub-team, a further analysis, or next month’s cycle breaks the rhythm that gives SIOP its value.
Curiosity over confidence. The best SIOP participants ask questions. They challenge assumptions. They want to understand why forecast accuracy is declining, not just note that it has. That curiosity is what drives the process improvement that makes next month’s SIOP better than this month’s.
Consistency over reactivity. SIOP works because it is a reliable rhythm. The organisations that benefit most from S&OP discipline are the ones where the cadence is sacred — where the process runs in good months and bad months, in crisis periods and calm ones. Leaders who suspend the process when things get difficult — when surely you need it most — destroy the institutional muscle the process was building. - The Multi-Site Complexity
One additional dimension worth naming, particularly for leaders with global or multi-site responsibility.
SIOP in a single-site, single-market business is already complex. Extend it across three sites, four product families, six commercial regions, and a mix of make-to-order and make-to-stock product, and the structural challenges multiply.
Demand signals arrive in different formats from different commercial teams. Supply constraints interact across sites in ways that a site-level planning process can’t see. Inventory sits in different locations, owned by different teams, counted by different systems. Premium freight gets booked locally and reviewed globally — but the accountability is always ambiguous.
Multi-site SIOP requires a formal hierarchy of planning forums. Site-level reviews feed regional or divisional integration. Divisional integration feeds executive SIOP. Each level has a defined scope, a defined frequency, and a defined set of escalation triggers that determine when a local issue becomes a cross-site decision.
Without that hierarchy, multi-site SIOP collapses into a monthly aggregation exercise — rolling up individual site plans and calling the result an integrated business plan. It isn’t. It’s a consolidated report. The integration — the genuine trade-off making across sites, across markets, across capacity pools — hasn’t happened.
Global SIOP is not harder than local SIOP by a matter of degree. It requires a fundamentally different architecture. - The Long View
Here is what a well-designed SIOP process produces — not in the first month, but over a sustained period of disciplined execution.
Forecast accuracy improves. Not because the market becomes more predictable — it doesn’t — but because the process of owning, measuring, and improving the forecast builds genuine planning capability in the commercial team.
Inventory reduces sustainably. Because the structural drivers of inventory have been understood and systematically addressed, and because the planning system no longer needs to carry large buffers to compensate for its own unreliability.
Premium freight becomes exceptional. Because constraints are visible three to four weeks ahead of when they crystallise, and the business has time to manage them without paying a premium for urgency.
Capacity decisions become proactive. Because the SIOP process provides a credible 12–18 month horizon, leadership can make investment decisions ahead of the need rather than in reaction to a crisis.
Leadership time shifts. The hours spent firefighting supply crises, reconciling planning gaps, and managing customer escalations reduce. That time becomes available for the things that actually build a better business — people development, strategic improvement, capability building.
And perhaps most importantly: the business develops a single version of the truth that functions and planners and commercial leaders actually trust. That trust is the foundation of effective cross-functional leadership. Without it, every conversation about resource, priority, and performance is contaminated by the suspicion that someone else’s numbers aren’t real.
A business with great SIOP doesn’t just plan better.
It makes decisions faster.
It executes more reliably.
It compounds capital efficiency year after year.
Final Thought
SIOP is not a planning problem.
It is a leadership design problem.
The meeting is the easy part. The infrastructure, the behaviour, the accountability, the integration — those are what determine whether your SIOP process is a genuine competitive advantage or an expensive monthly ritual that your best people endure with polite resignation.
Ask yourself three questions.
When was the last time your SIOP meeting changed a decision that had already been made?
When was the last time someone stood up in that meeting and said “the forecast is wrong and here’s why”?
When was the last time your SIOP output and your operational reality were still aligned at the end of the month?
If the answers make you uncomfortable, you already know what needs to change.
Start with the design.
The rest will follow.
Adam
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