Almost every due diligence, whatever the sector or deal size, eventually arrives at the same question: is this performance sustainable? Investors pay for future cash flows, not past profits. Historical results are useful only to the extent they indicate what the business will earn next year and the years after. A sharp rise in revenue, an expanding margin or a year of strong cash generation can each have causes that will not repeat.
This article sets out a practical framework for testing sustainability across three dimensions (growth, margins and cash) along with the use of management's forecasting track record and simple stress tests. It builds on the normalisation work covered in other articles and focuses on the forward-looking judgement. It is intended for investors, lenders and management teams presenting a business plan.
Key points at a glance
- Sustainability is tested separately for growth, margins and cash, because each can be flattered by different temporary factors.
- Splitting revenue growth into price, volume and mix shows how much comes from lasting demand.
- Margins can be inflated by favourable input prices, deferred maintenance, salary freezes or under-investment in people and systems.
- Management's past accuracy in budgeting is one of the best guides to the credibility of its forecast.
- Simple sensitivity tests on a few key drivers show how fragile the numbers are.
Why sustainability is the central question
Valuation multiples assume that the earnings they are applied to will continue and grow. If 20% of current EBITDA arises from conditions that will reverse within two years, a buyer applying a full multiple to it overpays. Sustainability is rarely visible in a single schedule; it emerges from patterns: how consistently data aligns across periods, how assumptions hold up against evidence and how explanations change when questioned.
Is revenue growth sustainable?
Price, volume and mix analysis
Revenue growth is broken down into price changes, volume changes and mix. Consider a company whose revenue rose from ₹80 crore to ₹100 crore (25% growth). Volumes rose from 40,000 tonnes to 42,000 tonnes, and the average realisation rose from ₹20,000 to about ₹23,810 per tonne.
| Driver | Calculation | ₹ crore |
|---|---|---|
| Volume effect | 2,000 tonnes × ₹20,000 | 4.0 |
| Price effect | 42,000 tonnes × ₹3,810 | 16.0 |
| Total growth | 20.0 |
Only 5% volume growth underlies the 25% revenue growth; the rest is price. If the price rise came from a spike in raw material prices passed on to customers, it may reverse when commodity prices fall, with little effect on profit but a large effect on reported revenue. If instead it came from a premium product launch, it is more durable. The diligence focus then moves to the cause of the price change.
Other growth tests
- Customer cohorts: revenue from customers acquired in each year, and how much of it is retained.
- Order book and pipeline: contracted and probable revenue for the next 12 months, with conversion rates from past pipelines.
- Market share: whether growth is faster than the market, and why.
- One-off demand: government orders, pre-buying before a price or tax change, or supply shortages at competitors.
Are margins sustainable?
Margins can be temporarily high because costs have been held back. Due diligence looks for costs that will need to "catch up":
- Deferred maintenance: repair and maintenance spend below the historical level or below what the asset base requires.
- Salary catch-up: wage increases below inflation or market levels, often visible in rising attrition.
- Under-staffing: vacant positions in finance, compliance or quality functions.
- Input cost windfalls: favourable raw material or energy prices, or long-term purchase contracts expiring soon.
- Compliance costs not yet incurred: environmental, safety or statutory requirements that will require spending.
Worked example: rebasing EBITDA for catch-up costs
Continuing the example, assume normalised EBITDA of ₹15 crore (15% margin). The review finds:
- Repairs and maintenance averaged 2.5% of gross block over the past five years but were 1.2% last year. On a gross block of ₹60 crore, the shortfall is ₹0.78 crore.
- Salary increases were frozen last year; a market-level increase of 8% on a wage bill of ₹10 crore adds ₹0.8 crore.
- A fixed-price power contract saving ₹0.6 crore a year expires in six months.
Sustainable EBITDA is ₹15.0 − 0.78 − 0.8 − 0.6 = ₹12.82 crore, a margin of about 12.8%. At 8x, the difference of ₹2.18 crore represents about ₹17.4 crore of enterprise value. Some of these items are adjusted in EBITDA; others, such as deferred maintenance, may instead be treated as a capex requirement or a debt-like item, depending on how the buyer models the business.
Is cash generation sustainable?
Cash flow can be strong in a year simply because of timing. The review checks whether:
- Working capital was released through stretched payables or unusual collections.
- Capital expenditure was below depreciation for several years, suggesting an ageing asset base.
- Customer advances or government incentives received in the year are recurring.
- Tax payments were lower due to incentives, losses or deductions that are expiring.
Practical point: A useful quick test is to compare capital expenditure with depreciation over five years. A ratio persistently below 1 in a capital-intensive business often means that future cash flow will need to fund catch-up investment.
How credible is management's forecast?
The best predictor of forecast reliability is past accuracy. Due diligence compares the budgets of the last two or three years with actual results, line by line. A management team that has consistently delivered within a few percent of budget earns more confidence than one whose forecasts have been missed by wide margins. The review also checks that the forecast is consistent with the historical analysis: if history shows 5% volume growth, a plan built on 20% needs specific evidence such as signed contracts or new capacity.
Stress-testing the numbers
Simple sensitivities on a few drivers show how resilient earnings are. For the example company with sustainable EBITDA of ₹12.82 crore on revenue of ₹100 crore:
| Scenario | Change | Effect on EBITDA (₹ crore) | Revised EBITDA (₹ crore) |
|---|---|---|---|
| Realisation falls 5% with no cost relief | Revenue −₹5 crore | (5.0) | 7.82 |
| Volumes fall 5% (contribution margin 30%) | Contribution −₹1.5 crore | (1.5) | 11.32 |
| Largest customer (15% of revenue) lost | Contribution −₹4.5 crore | (4.5) | 8.32 |
The table shows that the business is far more sensitive to price than to volume, and that customer concentration is a material risk. These findings guide both valuation and structure, for example through an earn-out tied to price realisation or protections around key customer contracts.
Frequently Asked Questions on Sustainability of Earnings
What does sustainability of earnings mean in due diligence?
It is the assessment of whether current revenue, margins and cash flow are likely to continue, after removing effects that are temporary, one-off or dependent on conditions that will change.
What is price-volume-mix analysis?
It splits revenue growth into the effect of changes in selling prices, changes in quantities sold and changes in the product or customer mix, to show how much growth comes from lasting demand.
What is deferred capex in due diligence?
It refers to capital or maintenance spending that has been postponed, making recent cash flow and margins look stronger. Buyers often adjust for it through EBITDA, capex forecasts or the price.
How is a management forecast tested in due diligence?
By comparing past budgets with actual results, checking consistency with historical trends and supporting key assumptions with contracts, pipelines and capacity data.
Why are sensitivity analyses used in due diligence?
They show how much earnings change if key drivers such as price, volume or a major customer move adversely, highlighting which risks matter most for valuation and structure.
Conclusion
Due diligence does not predict the future, but it can show how well a business is prepared for it. Breaking growth into its drivers, identifying costs that will need to catch up and testing cash flow for timing effects turns a general question into specific, measurable points.
When sustainability is supported by evidence, confidence in the numbers follows. When it is not, even strong reported results need to be priced and structured with care.
This article is intended for general information and knowledge sharing only and does not constitute professional advice or solicitation of any kind. Provisions are summarised as of September 2026. Readers should refer to the relevant provisions, regulations and judicial pronouncements for their specific facts.