पाठशाला Pathshala · हिसाब Hisāb, Unit economics · Lesson 27 · Scale
Working capital: the number that kills profitable companies
A company can show a profit every month and still run out of cash, because growth ties money up in receivables and stock. How to model the days and how fast profit alone can fund growth.
Pathshala, The Founder Library · 11 October 2026 · 8 min read
The most dangerous year in the life of a profitable company is often the one in which it doubles. Orders arrive, the P&L shows a profit every month, and the bank balance falls anyway, because each new order needs stock bought before it ships and credit extended before it is paid. The company is not losing money. It is lending it, to its customers and its warehouse, faster than it earns it.
This lesson defines the three numbers that decide working capital, shows how growth turns them into a cash requirement, works through a company that grows into a wall, sets out the Indian rules on payment days, and ends with the monthly line that catches the problem early.
Profit is not cash
Revenue is recognised when goods ship or a service is delivered. Cash arrives when the customer pays. Cost is recognised when the goods are sold. Cash leaves when the supplier is paid, which for stock can be months before the sale. The gap between those dates is working capital: the money a business must keep invested in receivables and inventory, less what its suppliers are effectively lending it through payables.
Neil Churchill and John Mullins set out the problem in the Harvard Business Review in 2001, in How Fast Can Your Company Afford to Grow?: a profitable company that tries to grow too fast can run out of cash, even if its products are great successes. Their argument is that growth has to be paced against the cash the business generates, and that the pace can be computed rather than guessed. The computation needs three numbers.
The three days that decide it
Debtor days, or days sales outstanding, is receivables divided by revenue, times 365: how long the average customer takes to pay. Inventory days is inventory divided by cost of goods sold, times 365: how long stock sits before it is sold. Creditor days, or days payables outstanding, is payables divided by cost of goods sold, times 365: how long the company takes to pay its suppliers. Debtor days plus inventory days less creditor days is the cash conversion cycle, the number of days between paying for stock and being paid for it.
A software company selling annual plans paid upfront can have a negative cycle: customers pay before the service is delivered, and the company holds their cash. A distributor selling to modern trade on 60-day terms, holding 75 days of stock and paying suppliers in 45, has a cycle of 90 days. Every rupee of its annual revenue requires about 22 paise of working capital, permanently, for as long as the terms hold.
Compute the three days from the balance sheet at each month-end, using the last three months of revenue and cost annualised, not the year’s total; a seasonal business will otherwise read the wrong number for most of the year. Compute them for each large customer too. One retail chain paying in 120 days can move the company’s debtor days by twenty on its own.
How growth eats cash
Working capital scales with revenue. If each rupee of annual revenue ties up 22 paise, then adding ₹10 crore of annual revenue ties up ₹2.2 crore more, and that cash has to be found before the extra revenue produces its profit. A company earning an 8 per cent net margin makes 8 paise on each rupee of the larger revenue; it needs 22 paise of working capital for each rupee of the growth.
That gives the self-funding growth rate. Cash generated in a year is net margin times next year’s revenue, less working capital per rupee times the increase in revenue. Set it to zero and solve: the fastest growth profit can fund is net margin divided by working capital per rupee less net margin. At an 8 per cent margin and 22 paise of working capital per rupee, that is about 58 per cent a year. Grow faster and the company must borrow, raise equity or shorten its days. Grow much faster and it can run out of cash in a year of record profits.
The same arithmetic explains why a margin improvement matters twice in a working-capital business: it adds profit, and it raises the growth the company can fund. And it explains why a new channel with longer payment terms, a modern-trade chain or an enterprise customer, can be a cash problem even when it is a profit opportunity.
One company, growing into a wall
A Jaipur home-textiles brand sells to retail chains and online marketplaces. It makes ₹20 crore of revenue a year at a 35 per cent gross margin and an 8 per cent net margin. Customers pay in 60 days on average, stock sits for 75 days and suppliers are paid in 45. Its working capital is about ₹4.4 crore. A large chain offers a contract that would lift revenue by 60 per cent this year.
At 60 per cent growth the company earns ₹2.6 crore of profit on ₹32 crore of revenue and needs ₹2.6 crore more working capital to carry the extra ₹12 crore. It ends the year with about ₹5 lakh less cash than it started, having made the best profit in its history. Now set debtor days to 90, the chain’s actual terms. The fastest growth profit can fund drops to 36 per cent, and the same year consumes about ₹1 crore of cash.
Move the days one at a time and compare their effect. Ten fewer debtor days are worth more than ten more creditor days here, because receivables are carried at the full selling price while payables are carried at cost. Inventory days sit between the two. That ordering is the order in which to work on them.
A company does not run out of cash because it is unprofitable. It runs out because it grew faster than its days allowed.
The Indian rules on days
Two Indian rules set limits on creditor days, and both cut both ways. Under the MSMED Act, 2006, a buyer must pay a micro or small enterprise supplier within the agreed period, which cannot exceed 45 days from acceptance of the goods or services. The Ministry of MSME’s Samadhaan portal records that a buyer who pays late owes compound interest with monthly rests at three times the bank rate notified by the RBI, and that the delayed-payment provisions sit in sections 15 to 24 of the Act. A supplier can file a case there, before a facilitation council.
The tax rule adds teeth. Section 43B(h) of the Income-tax Act, 1961, inserted by the Finance Act, 2023 with effect from 1 April 2024, allows a deduction for a sum payable to a micro or small enterprise beyond the section 15 time limit only in the year it is actually paid. The rule continues under the Income-tax Act, 2025 as section 37(2)(g), as the finance ministry confirmed in a Rajya Sabha reply in July 2026. A company cannot stretch micro and small suppliers past 45 days to fund its own growth without paying for it in interest and tax. Both rules were checked on 11 October 2026; the [Section 43B(h) lesson](/library/section-43b-h-paying-msme-vendors-on-time) covers them in full.
The other edge: a startup registered on Udyam as a micro or small enterprise is protected by the same rules when it sells to large companies. Its customers owe it interest after 45 days, and their tax deduction depends on paying on time. Many founders never mention this in a collections conversation. It is worth mentioning, politely, with the registration number on every invoice.
Six ways to shorten the cycle
Bill earlier and more often. Invoice on dispatch rather than at month-end, and on milestones rather than on completion. Collect actively. A named owner for each large receivable, a call on day one of overdue and a weekly ageing review usually take ten days off debtor days within a quarter. Price for terms. Offer a small discount for payment within 15 days, or a price premium for 90-day terms; either makes the cost of credit visible to the customer. Discount receivables. A micro or small supplier can discount its invoices on large buyers on TReDS, the trade receivables discounting system, turning a 90-day receivable into cash within days at a cost; the Budget 2026–27 measures extend it by mandating TReDS for central public sector purchases from MSMEs. Check the discount rate against the margin first.
Hold less stock. Inventory days fall with fewer SKUs, smaller and more frequent purchase orders, and selling the slow movers rather than storing them; the [vendors lesson](/library/vendors-procurement-contracts-you-keep-renewing) covers the supplier terms that make smaller orders possible. Negotiate creditor days where the law allows, with large suppliers rather than small ones, and in exchange for something the supplier values, such as volume commitments or faster acceptance.
The monthly working-capital line
On the fifth working day of each month, after the books close, compute debtor, inventory and creditor days and the cash conversion cycle, for the company and for the five largest customers. Put the last six months beside them. Then compute working capital per rupee of annual revenue and the self-funding growth rate at the current net margin, and compare it with the growth in the plan.
If planned growth is above the self-funding rate, the gap has to be financed, and the conversation about how, a working-capital line, receivables discounting, equity, or slower growth, should happen this month rather than when the balance is low. Feed the days into the [thirteen-week cash forecast](/library/thirteen-week-cash-forecast) so that the forecast and the plan use the same numbers. Before accepting any large contract, run its payment terms through the same arithmetic. A contract that adds revenue and removes cash is a loan to the customer, and should be priced like one.
Nothing here is legal, tax or investment advice. The Jaipur company is illustrative; its figures are the figure’s defaults so that every number in the text can be reproduced. Payment and tax rules were checked on 11 October 2026 and change; confirm them before relying on them.
Sources
- Neil C. Churchill and John W. Mullins, How Fast Can Your Company Afford to Grow?, Harvard Business Review, May 2001 — A profitable company that tries to grow too fast can run out of cash; growth paced against cash generation.
- Income Tax Department, Section 43B, Income-tax Act, 1961 — Clause (h): sums payable to a micro or small enterprise beyond the MSMED Act section 15 time limit deductible only on payment; inserted by the Finance Act, 2023 from 1 April 2024. Checked 11 October 2026.
- Ministry of MSME, MSME Samadhaan: Micro and Small Enterprises Facilitation Council — Payment within 45 days of acceptance; compound interest with monthly rests at three times the RBI bank rate; sections 15–24 of the MSMED Act, 2006. Checked 11 October 2026.
- Press Information Bureau, Ministry of MSME, reply in Rajya Sabha on MSME registrations and support, 30 March 2026 — Budget 2026–27 measures include mandating TReDS for CPSE purchases from MSMEs and CGTMSE-backed guarantees for TReDS invoice discounting.
- TaxGuru, Finance Ministry clarifies Section 43B(h) 45-day MSME payment rule, July 2026 — Reports the Rajya Sabha reply of 21 July 2026; the provision corresponds to section 37(2)(g) of the Income-tax Act, 2025.