Sell Side Due Diligence: Prove Your EBITDA Forecast

EBITDA Forecast Validation Starts in the Value Creation Plan

Is your EBITDA coming from demand you can prove? Only if a buyer can trace it. A private equity operational due diligence team tests two things: whether the growth is in the forecast, and whether the plant has the capacity to deliver it. A shrug on either one puts a discount on the EBITDA story. The evidence isn’t assembled at exit. It comes from forecasting and S&OP running inside the value creation plan, early enough that the results show before the sale process begins.

Buyers are not getting easier. Simon-Kucher’s October 2026 study of 215 PE executives found that 30% rank exits at target valuations as the hardest part of today’s environment, and it notes that buyers underwrite a history of proof, not a last-minute snapshot. CLA reports that leading firms start exit prep 12 to 18 months out because EBITDA adjustments get challenged and forecasts must match operational reality. That 12-to-18-month window is the last stage. The record a buyer wants to see comes from the hold.

The failure buyers screen for

We see one pattern more than any other: strong demand, a good product, and a plant that can’t ramp. Planning, supply chain, and capacity were never lined up to the demand, and it breaks both ways. Some manufacturers under-forecast. The demand arrives and the capacity isn’t there to fill it. Others over-forecast and burn capacity building product nobody needed yet. Either way the EBITDA forecast misses. That is why EBITDA forecast validation, a buyer’s test of whether your number will hold, starts with the demand forecast. A diligence team walks the chain:

Step 1: Start with the customer

They start where the money starts: who is ordering, how often, and what customers expect on delivery and quality. They look at backlog, order history, customer concentration, and on-time-in-full performance. Growth that rests on one customer, or on delivery performance the plant doesn’t hit today, is growth at risk. Customer-level data that shows where growth comes from, and whether it lasts, carries weight.

Step 2: The forecast and the S&OP process

S&OP is a value creation lever before it’s a diligence exhibit. Demand forecasting for manufacturers usually breaks in two places: how accuracy is measured, and how the forecast meets the budget. The first number we ask for is forecast accuracy, and how it’s measured matters more than the number. Many companies measure against last month’s forecast. By then they can already see the month’s orders, so they look accurate. Measure against the forecast made when materials had to be committed, often three months back, and the picture changes. At one growing manufacturer, we ended up measuring at a two- to three-month lag, because that’s when materials, equipment, and people have to be committed.

Then comes the budget. A diligence team looks for a forecast that keeps moving while the annual number never does. Say a team misses January by $1 million. It spreads the shortfall across the rest of the year and holds the budget. February, same thing. The back half keeps growing with no plan behind it. That’s the hockey stick, and it ends in November with too much inventory, wasted capital, and time and people spent on product nobody needed.

S&OP breaks the cycle by keeping the demand plan separate from the budget. Sales says what it truly expects over the next 12 months. Then you stack that against the budget. The gap forces the real conversation: which customers, which markets, what help? At one building products manufacturer, sales over-forecast by about 10% every month. Leadership wanted sales held to the number, so we planned materials about 10% lower, closer to reality.

The payoff reaches cost structure. S&OP shows where demand is heading so staffing and spend adjust before a miss. A packaging manufacturer tied its forecast to point-of-sale data and trimmed SKUs. Accuracy rose from about 55% to about 75%, inventory on one product line fell by $1 million, and case fill rates improved while inventory dropped. Product-family accuracy at manufacturers commonly sits between 55% and 70% before this work.

Step 3: Capacity and line balance

Last, they test whether the plant can make what the forecast promises. They compare actual run rates with theoretical maximum, find the bottleneck, and check whether sales, supply chain, and operations forecasts drive capacity decisions. In one TBM diligence case, recalculating capacity showed key coaters running under 25% of available hours, which exposed idle capacity and narrowed the capex request to a few targeted items.

For capital-heavy plants, we start with OEE and uptime: setup times, maintenance, and quality downtime. Lines out of balance mean the real constraint may not be where the plan assumes. And connected data matters. One global manufacturer absorbed more than $1 million in expedited air freight A monthly S&OP cycle with a live capacity model now surfaces those constraints weeks ahead.

What to build during the hold, and have ready before a process starts.

Put each item in the value creation plan with a time-to-EBITDA. Start with forecast accuracy history, because a year of locked forecasts can’t be created after the process starts. Three things, in this order:

Forecast accuracy history. A year or more of locked monthly forecasts measured against actuals at the right lag, with bias tracked by product family.
A documented S&OP cadence. A monthly cycle with pre-reconciled demand, supply, and finance views, an executive session that makes decisions, and a closed loop to production and purchasing.
Capacity tied to the forecast. A constraint map by line, and a capacity plan that updates when the forecast does.

If the clock is already running, move on the quickest returns first. My recommended 90-day value creation list is short: rebid purchased materials, right-size the cost structure to the forecast, and push the constrained work center that has a backlog. The 12-month work is lean across the work cells. Sponsors know how to find revenue. The question is whether operations can deliver it.

If the original value creation plan has run its course, write the second one around these three items. If a process is 12 to 24 months out, start with Phase Zero. It’s the diagnostic that finds which lever matters and sizes it in weeks.

Frequently Asked Questions

What is sell side due diligence, and why does it matter for manufacturers?

Sell side due diligence is the seller’s own review of its business before a sale process, run to find what a buyer’s team will test. For manufacturers, buyers test whether growth is in the forecast and whether the plant has the capacity to deliver it. Gaps found early get fixed during the hold. Gaps found late get discounted.

When should a manufacturer start validating its EBITDA forecast before an exit?

Start during the hold, inside the value creation plan, not at exit. CLA reports that leading firms begin exit prep 12 to 18 months out, but the core evidence takes longer. Buyers want a year or more of locked monthly forecasts measured against actuals, and that history can’t be created after a process starts. Build forecast accuracy history first, then a documented S&OP cadence, then capacity tied to the forecast.

How do buyers test whether a manufacturer’s EBITDA forecast will hold?

Buyers trace it in three steps. They start with the customer: order history, backlog, customer concentration, and on-time-in-full performance. They then test the forecast and S&OP process, including whether accuracy is measured at the lag when materials were committed and whether the demand plan is kept separate from the budget. Last, they compare actual run rates with theoretical maximum to see whether the plant can make what the forecast promises.

Meet the Expert

Brian Cromer

Managing Director, Global Supply Chain PracticeEmail Brian

Brian Cromer is Managing Director of TBM’s Global Supply Chain practice where he helps clients to make operational improvements, reduce working capital and improve service levels while lowering the overall cost to serve.

Topics in this Post

Key Takeaways

Buyers pay for EBITDA they can trace. A diligence team tests whether growth is in the forecast and whether the plant has the capacity to deliver it, starting with the customer.
How forecast accuracy is measured matters more than the number. Measure at the lag when materials were committed, and use S&OP to keep the demand plan separate from the budget.
The proof is built during the hold. Put forecast accuracy history, an S&OP cadence, and capacity tied to the forecast in the value creation plan, each with a time-to-EBITDA.

Schedule a 15-minute call with your Advisor