Your biggest customer just doubled their order, and next year's sales forecast jumps 20 percent, from $500,000 to $600,000. You should be celebrating — but your gut says to check the bank balance first. That instinct is correct. Every extra dollar of sales drags assets behind it: more inventory on the shelf, more receivables waiting to be collected, maybe another machine or another pair of hands. Those assets have to be paid for with something, and that something is either money your business generates on its own or money you raise from the outside. Additional Funds Needed — AFN — is the equation that tells you exactly how big the outside check has to be, months before you need to sign it.
Why growth eats cash even when you are profitable
Growth creates a timing gap that surprises first-time founders. You buy the inventory, pay the workers, and ship the goods weeks or months before the customer pays you. Your income statement shows a profit on the sale the day it ships. Your bank account does not see the cash until the invoice clears. Multiply that gap across 20 percent more sales and a profitable, growing business can run completely dry — accountants call this growing broke, and it kills more healthy companies than unprofitability does.
AFN exists to quantify that gap before it opens. It takes your sales forecast and answers one question: after counting everything your growth funds by itself, how much outside money must you still arrange? Run it during planning season and you walk into the bank with a specific number and a reasoned case, instead of discovering the shortfall from an overdraft notice.
The AFN equation in plain English
At its simplest, the equation is three terms:
AFN = Required increase in assets − Spontaneous increase in liabilities − Increase in retained earnings
Read it as a story in three acts. Growth demands new assets — that is the bill. Some financing arrives automatically as your payables and accruals swell alongside sales — that is the discount. And some comes from profit you keep in the business rather than paying out — that is the down payment. Whatever is left over is the amount you must raise from lenders or investors.
The percent-of-sales method turns that story into arithmetic by assuming assets and certain liabilities grow in fixed proportion to sales. If last year you needed 80 cents of assets for every dollar of sales, the method assumes next year needs the same 80 cents on every new dollar. That gives the expanded form you will see in every corporate finance textbook:
AFN = (A/S0) × ΔS − (L/S0) × ΔS − M × S1 × RR**
Each symbol earns its place:
- A* — the assets required to support your sales. Usually total assets, unless you are adjusting for spare capacity (more on that below).
- S0 — your current sales, the base year.
- ΔS — the forecast increase in sales, which is projected sales minus current sales.
- L* — spontaneous liabilities: payables and accruals that rise on their own as sales rise.
- M — your profit margin, net income divided by sales.
- S1 — your forecast sales for the coming year.
- RR — the retention ratio, the share of net income you keep. It equals one minus your dividend or owner-draw payout ratio.
The ratio A*/S0 has its own name — the capital intensity ratio — and it is worth knowing, because it is the single biggest driver of the answer. A business that needs 80 cents of assets per sales dollar will always thirst for more outside funding than one that needs 30 cents, at the same growth rate and margin.
Spontaneous liabilities: the free financing hiding in your payables
The distinction between spontaneous and negotiated liabilities is the hinge the whole formula swings on, so get it right. A spontaneous liability increases automatically when sales increase, with no new decision and no loan application. Accounts payable is the classic case: sell 20 percent more and you order roughly 20 percent more from suppliers, so the balance you owe them swells on its own. Accrued wages and accrued taxes behave the same way — more activity means bigger accruals at each month-end.
Notes payable, bank loans, bonds, and new equity are not spontaneous. None of them rises by itself when sales rise; each requires a deliberate financing decision. That is precisely why they are excluded from L* — AFN is the measure of how much of exactly those discretionary sources you must arrange. The most common beginner mistake is stuffing a bank line of credit into spontaneous liabilities because "we always draw it when sales grow." That understates AFN and manufactures a funding plan out of a habit. If it takes a signature, it is not spontaneous.
A worked example: the $41,200 growth check
Take a wholesale distributor with current sales of $500,000, forecasting 20 percent growth to $600,000. Its balance sheet shows $400,000 in assets and $50,000 in spontaneous liabilities — $35,000 of accounts payable plus $15,000 of accrued wages and taxes. Its profit margin is 8 percent, and the owners take 40 percent of profit as draws, retaining 60 percent.
Step one is the bill — the assets growth demands. The capital intensity ratio is $400,000 divided by $500,000, or 0.80. Multiply by the $100,000 sales increase: $80,000 of new assets required.
Step two is the discount — the spontaneous financing. The spontaneous-liabilities ratio is $50,000 divided by $500,000, or 0.10. Multiply by the same $100,000 sales increase: $10,000 that funds itself.
Step three is the down payment — the retained profit. Margin of 8 percent on forecast sales of $600,000 gives $48,000 of net income, and retaining 60 percent keeps $28,800 inside the business.
AFN = $80,000 − $10,000 − $28,800 = $41,200. That is a positive AFN: the distributor must arrange $41,200 from outside — a term loan, a bigger credit line, an equity injection — or change one of the inputs. The number is specific enough to act on: it prices the loan request, sizes the credit line increase, and tells the owners exactly what their 40 percent draws are costing the growth plan.
When AFN goes negative: the surplus problem
A negative AFN is not an error. It means your internal funds exceed what your asset growth requires — you will finish the growth year with cash left over. Run the same distributor with a 15 percent margin and full retention instead: retained earnings contribute 0.15 × $600,000 × 1.0 = $90,000, and AFN becomes $80,000 − $10,000 − $90,000 = −$20,000. That $20,000 surplus can repay debt, fund a dividend, build a cash buffer, or bankroll growth beyond the forecast.
Negative AFN is the normal state of mature, cash-generative businesses — high margins, modest capital needs, disciplined payouts. Service businesses get there easily because they carry little inventory and few receivables per sales dollar. If your AFN is persistently negative, the interesting question flips: your growth plan is under-ambitious for your cash engine, and the surplus should be working harder somewhere.
Five levers that shrink your AFN
The equation is also a menu. Every term is something management can move, and a founder staring at a $41,200 gap has five handles to pull before calling the bank.
1. Grow a little slower
AFN scales with the sales increase, so trimming the growth target trims the gap almost proportionally. The extreme version of this lever has a name: the self-supporting (or sustainable) growth rate — the fastest you can grow with AFN at exactly zero, funding everything internally. Knowing that rate turns "can we afford 20 percent?" from a guess into arithmetic.
2. Squeeze more sales from your existing assets
A lower capital intensity ratio means less AFN at any growth rate. Collect receivables faster, trim slow-moving inventory, sell idle equipment, and put spare capacity to work before buying anything new. An asset-turnover drive is often the cheapest financing a business ever raises, because the assets are already paid for.
3. Stretch spontaneous liabilities — carefully
Longer supplier payment terms raise L*/S0 and directly reduce AFN. Renegotiating from net-30 to net-45 across your supplier base is genuine, interest-free financing. The caution is that suppliers are partners, not banks: pay late without agreement and you trade a funding gap for damaged relationships, lost discounts, and worse terms next year. Negotiate the terms, then honor them.
4. Widen your profit margin
Every extra point of margin flows through retained earnings into a smaller AFN. Price increases, mix shifts toward higher-margin work, and cost discipline all pull this lever. Margin improvement is the only lever that simultaneously funds growth and makes the business more valuable — which is why lenders love to see it in the plan behind the loan request.
5. Retain more of what you earn
Cutting the owner-draw or dividend payout ratio during growth years keeps cash where the growth needs it. This is the lever founders resist most and bankers ask about first: a business requesting a loan while paying out 80 percent of its profit is asking the bank to fund the owners' lifestyle. A temporary payout cut is often the difference between needing a loan and self-funding.
Where the formula lies: excess capacity and lumpy assets
The percent-of-sales method assumes two convenient things that are rarely both true: that you operate at full capacity, and that assets grow in smooth proportion to sales. Reality deviates in three predictable ways, and each has a standard fix.
Excess capacity is the big one. If your plant, warehouse, or team runs at 70 percent of capacity, sales can grow substantially with zero new fixed assets — but the basic formula charges you 80 cents of new assets on every new sales dollar anyway, overstating AFN. The fix is to split fixed assets out of A*: forecast the smooth items (receivables, inventory, payables) by percent of sales, and add fixed assets only when forecast sales exceed what current capacity can support.
Lumpy assets break smoothness from the other side. You cannot buy half a delivery van or lease a third of a warehouse — fixed assets arrive in indivisible chunks, so actual asset needs follow a staircase while the formula draws a straight line. Near a step, AFN understates the true cash need. The fix is judgment: if growth pushes you over a capacity step, budget the whole chunk and treat the formula's smooth number as a floor, not a forecast.
Economies of scale bend the ratios themselves. As you grow, inventory systems get leaner, purchasing gets sharper, and fixed costs spread thinner — A*/S0 drifts down rather than holding constant. The formula assumes yesterday's ratios; a thoughtful forecast shades them toward where scale is taking you.
None of this invalidates AFN. It makes AFN the starting point of the conversation rather than the final answer: run the textbook number first, then adjust for your capacity, your lumps, and your scale.
Pulling your AFN ratios straight from your ledger
AFN is only as honest as the balance sheet behind it, and the most practical upgrade you can make is structural: keep spontaneous liabilities in accounts that are visibly separate from negotiated debt. When accounts payable and accrued wages sit apart from bank loans and notes payable, your A*/S0 and L*/S0 ratios pull straight from real balances instead of year-end guesses — and next year's forecast takes minutes rather than a weekend. If you keep your books in plain text, the Beancount documentation shows how to set up this account structure from scratch.
The pattern looks like this: sales on credit swell receivables (an asset increase), restocking on supplier terms swells payables (a spontaneous increase), and the wage accrual follows headcount — while the negotiated loan balance does not move a cent on its own:
2026-01-01 open Assets:Cash:Checking USD
2026-01-01 open Assets:Receivable USD
2026-01-01 open Assets:Inventory USD
2026-01-01 open Liabilities:Payable USD
2026-01-01 open Liabilities:Accrued-Wages USD
2026-01-01 open Liabilities:Bank-Loan USD
2026-01-01 open Equity:Opening-Balances USD
2026-01-01 open Income:Sales USD
2026-01-01 open Expenses:Cogs USD
2026-01-01 open Expenses:Wages USD
2026-02-01 * "Opening balances for the growth quarter"
Assets:Cash:Checking 50,000.00 USD
Assets:Receivable 40,000.00 USD
Assets:Inventory 30,000.00 USD
Liabilities:Payable -18,000.00 USD
Liabilities:Accrued-Wages -7,000.00 USD
Equity:Opening-Balances -95,000.00 USD
2026-02-28 * "February sales on credit"
Assets:Receivable 60,000.00 USD
Income:Sales -60,000.00 USD
2026-02-28 * "Cost of February sales"
Expenses:Cogs 36,000.00 USD
Assets:Inventory -36,000.00 USD
2026-02-28 * "Restock inventory on supplier credit"
Assets:Inventory 44,000.00 USD
Liabilities:Payable -44,000.00 USD
2026-02-28 * "Accrue February wages"
Expenses:Wages 11,200.00 USD
Liabilities:Accrued-Wages -11,200.00 USDFebruary's growth is all there in miniature: receivables up $60,000 on the asset side, payables and wage accruals up $55,200 on the spontaneous side, and the bank loan untouched. With accounts organized this way, each month-end balance sheet hands you fresh A* and L* totals, and your AFN forecast is always one spreadsheet row away from reality.
Run the equation on your own forecast this week. Pull last year's sales, this year's target, your margin, and your payout ratio — four numbers you already have — and the formula will hand you the size of the check before anyone asks you to sign it. If the answer is positive, you now know exactly which of the five levers to pull first. If it is negative, you have just proven your growth funds itself, which is the best sentence a funding conversation can start with.
