Base Case: How the Central Case Is Set and What It Must Not Be
A base case is the central set of assumptions a plan or a valuation is built on: the outcome considered most likely, with every assumption defendable on its own and consistent with the others. Everything that follows is measured against the base case, so the base case is not the hoped-for case, not the number promised to a lender, and not a cautious figure with hidden cushions.
The base case is unlike the measures around it: no formula, no index, no ratio. A base case is a standard of honesty, and honesty turns out to have rules that can be checked. Every scenario, sensitivity and stress test built later is measured as a distance from the base case, so a bent base bends everything built on it, silently and in the same direction.
What is a base case, and what is it for?
Base cases are already familiar from household life. A monthly household budget written on the salary actually expected, not the increment being hoped for and not a fearful understatement, is a base case. Its job is to be the honest centre: the anchor every other number is measured against. Asking later what if the increment does come, or what if the scooter needs repairs, measures distances from that centre, and the distances only mean something if the centre was honest.
A business or an analyst does exactly this at larger scale. Tessora Weaves, an invented exporter, needs one central view of next year before it can plan borrowings, hiring or anything else. The central view is the base case, and only a number with a stated reason earns a place in it.
A household budgets next month on this month's salary plus the Diwali bonus they are fairly hopeful about. What kind of case did they just write?
What does most likely actually require of each assumption?
A reason, stated, for next year specifically. Last year's number is a fact; it is not a reason. Revenue grew 12 per cent last year states what happened when last year's conditions held. To put 12 per cent in the base case requires a why that survives being said out loud: confirmed orders, signed programmes, capacity that exists. The test for every single assumption is one question: could this number be defended, alone, to a sceptical stranger, without pointing at the others?
An analyst sets revenue growth at 12 per cent because that is what last year delivered. Is that a base case assumption?
Why must the assumptions be consistent with each other?
Because assumptions describe one world, together. Here is the trap: three assumptions can each pass the defend-it-alone test and still be nonsense as a set. Growth of 15 per cent, no new hiring, and flat costs are three defensible sentences describing an impossible world. The growth requires capacity that the other two assumptions forbid. So every assumption faces two gates, not one: defendable alone, then consistent with the others. Most bent base cases die at the second gate, and most people never run it.
A plan assumes 15 per cent growth, no new hiring, and flat costs. Each is defensible alone. What is wrong?
What must a base case never be?
Three corruptions, each an answer to the wrong question. The hope case answers what would be wonderful. It is the founder's favourite, growth where growth is wished for. The pitch case answers what the listener needs to hear, the case built backwards from the loan amount or the valuation someone wants. The padded case answers what is safe to promise, every line quietly trimmed. Padding feels virtuous, and feeling virtuous is exactly what makes padding dangerous. Only the base case answers what is most likely.
To support a bigger working capital line, next year's growth is written as 15 per cent when the confirmed programmes support 5. Which corruption is this, and who pays for it later?
Why is padding a corruption too?
Because a cushion the reader cannot see is indistinguishable from information. If every line is trimmed 5 per cent to be safe, the trims compound into a picture that is confidently, invisibly wrong, and everything measured from it inherits the bend. The downside case built on a padded base is doubly pessimistic; the upside looks absurdly far away; and one day someone makes a real decision, pricing, hiring, borrowing, off cushions they cannot see. Safety, when it is wanted, belongs in a margin stated openly beside an honest number. Hidden safety is just error with good intentions.
An analyst quietly sets every assumption slightly cautious, to be safe. What happens when this base feeds the scenario work built on it later?
What is Tessora Weaves' base case for next year?
Here it is, assumption by assumption, each with its reason, and reconciling with the profit build covered under leverage. Revenue up 5 per cent to Rs 50,40,00,000, on Meridian Retail Group's confirmed programme and flat orders from Nordhaven Stores and Calluna Home. Variable costs held at 50 per cent on contracted yarn. Fixed costs flat: current capacity carries the volume. Interest unchanged at Rs 1,10,00,000. Work it through: contribution Rs 25,20,00,000, earnings before interest and tax (EBIT) Rs 7,20,00,000, profit before tax (PBT) Rs 6,10,00,000. No line carries a hidden cushion; where the business wants safety, it will state a margin openly in the cases built next.
| Assumption | Value | The reason, stated |
|---|---|---|
| Revenue | Rs 50,40,00,000 (+5 per cent) | confirmed programme, flat other orders |
| Variable costs | 50 per cent of revenue | contracted yarn prices, same mix |
| Fixed costs | Rs 18,00,00,000 | current capacity carries the volume |
| Interest | Rs 1,10,00,000 | no new borrowing planned |
| PBT, the base | Rs 6,10,00,000 | the anchor every case ahead measures from |
Check Tessora Weaves' base against the two gates. Which assumption would fail first if revenue were set at +15 per cent instead of +5?
How does a base case stay honest through the year?
A base case is written once and then attacked by reality monthly, so honesty needs a maintenance routine. The routine has three moves. Compare: each month, lay actuals against the base and name the gap. Explain: attribute the gap to a specific assumption, orders behind, yarn dearer, a delayed programme, never to "timing" or "market conditions", the two phrases that explain everything and mean nothing. Revise with a reason: when the evidence says an assumption was wrong, change it in writing, with the why, dated. A base case revised on evidence stays an anchor; one revised to avoid embarrassment becomes a diary of wishes.
The discipline this builds is the one skill every analyst is actually paid for: separating being wrong from being dishonest. Wrong is normal and survivable; the year betrays honest bases all the time. Dishonest is fatal, and the monthly written record is what keeps the two distinguishable.
Six months in, actuals run well behind the base and the evidence says the demand assumption was wrong. What is the honest move?
The error that gets made, and what it costs
The pitch case presented as the base. To support a bigger line, next year's growth is written as 15 per cent, and the lender prices the loan against it: repayment schedule, covenants, the lot. The year delivers 5. Five was always the honest number. Every covenant and every instalment was measured from a centre that was never the centre, and the gap lands in the exact months the schedule assumed it would not.
The cost is not the optimism; it is that the repayment calendar believed it.
A base case turns out wrong: the year delivers 2 per cent against a base of 5. Was the base case dishonest?
References
| Source | Document | Where |
|---|---|---|
| Securities and Exchange Board of India (SEBI) | Disclosure language on projections in offer documents | sebi.gov.in |
Tessora Weaves Private Limited, Meridian Retail Group, Nordhaven Stores and Calluna Home are invented.
Educational material. Not advice on any investment, tax, budget or market position.