The operating model: three statements, linked
Northwind's fourth quarter as three linked statements: drivers in, cash derived, and a balance sheet that balances without a plug.
A P&L forecast says whether the company will make money. It can't say whether the company will have money, because profit and cash differ by working capital and by spending that isn't expense. An operating model forecasts all three statements, linked. Profit flows into retained earnings, balances like receivables come from drivers, and cash is derived from the cash flow statement. It's never typed. If the links are right, the balance sheet balances every month without a plug.
- DriversGrowth, margins, costs, days.
- P&LRevenue less costs.
- Working capitalReceivables, stock, payables from days.
- Cash flowNet income plus the changes, by the indirect method.
- This lessonBalance sheetOpening cash plus the cash flow. Assets equal liabilities plus equity.
Northwind's Q4 drivers
Northwind Traders, Inc. — balance sheet
As of September 30, 2026 · USD
| Current assets | |
| Cash — operating | 35,352.60 |
| Accounts receivable | 8,000.00 |
| Allowance for credit losses | (160.00) |
| Inventory | 1,000.00 |
| Prepaid insurance | 6,600.00 |
| Total current assets | 50,792.60 |
| Vehicles | 24,000.00 |
| Accumulated depreciation — vehicles | (500.00) |
| Total assets | 74,292.60 |
| Liabilities | |
| Accounts payable | 6,000.00 |
| Payroll liabilities | 2,335.20 |
| Accrued liabilities | 450.00 |
| Sales tax payable | 760.00 |
| Deferred revenue | 3,000.00 |
| Dividends payable | 500.00 |
| Total liabilities | 13,045.20 |
| Common stock | 60,000.00 |
| Retained earningsSeptember's net income, less the dividend declared | 1,247.40 |
| Total equity | 61,247.40 |
| Total liabilities and equity | 74,292.60 |
Read October. Net income is 2,632.40 and operating cash flow is (2,508.77). The gap is working capital you can name. Receivables grow because the trade invoice is now a full month outstanding ((14,514.84)). The deposit Northwind banked in September is earned in October with no cash moving ((3,000)). The supplier, on 30-day terms, funds part of it (11,289.80). By December the pattern settles, and operating cash flow is 5,117.11 on net income of 4,192.96.
Cash is the last line computed, never the first typed. If the balance sheet needs a plug to balance, the model is wrong somewhere upstream.
Wrong
Closing cash = opening cash + net income October: 35,352.60 → 37,985
Right
Closing cash = opening cash + operating, investing and financing cash flow October: 35,352.60 → 32,343.83
The shortcut assumes every sale is collected and every cost paid in the same month. Northwind's October proves it wrong by thousands of dollars.
Driver-based, three statements linked
- Good at
- Change one assumption and every line moves
- Balances by construction, so errors show
- Watch for
- Takes longer to set up
- Every driver has to be defensible
- Best for
- Any forecast someone will make decisions from
Line-by-line, P&L only
- Good at
Fast
- Watch for
- Cash doesn't tie to anything
- Every change means retyping cells, and they drift
- Best for
- A first rough cut, never a board pack
Where this lesson's rules come from
The sources behind this lesson's requirements, by kind. Background reading explains; it is never the authority for a rule. Anything marked as a convention is ours, not the rule-maker's.
- US GAAP
- ASC 230-10-45-28, -45-29 (opens in a new tab)The indirect method, and what it must separately reportFree after registration
- Background reading — not an authority
- Wikipedia, “Financial modeling” (opens in a new tab)Financial modeling — backgroundFree to read
The full map is in US GAAP, and where these rules come from.
The words this lesson teaches
Each links to its glossary definition, which also names the authority behind it and the components that render it.
- Operating modelA forecast in which the income statement, balance sheet and cash flow statement are linked: profit flows to retained earnings, working-capital balances come from assumptions, and cash is derived from the cash flow — never typed — so the balance sheet balances by constructionConvention
- DriverAn input assumption a forecast line is computed from — a growth rate, days of receivables, headcount, price — rather than typed. Changing a driver moves every line that depends on itConvention
- ForecastThe current best estimate of a period's results or cash, revised as actuals arrive. A budget says what was planned; a forecast says what is now expectedConvention
- Cash flow statementWhere the cash went in a period — receipts and payments classified as operating, investing or financing, reconciling opening to closing cash, with operating cash also reconciled to net income
- Retained earningsAccumulated net income not distributed to owners — where the P&L lands on the balance sheet
- Working capitalWorking capital is a liquidity and working-capital metric, calculated as Current assets − Current liabilities.Convention
- Indirect methodPresenting operating cash flows by starting from net income and adjusting for non-cash items and changes in working capital — the method most entities use. ASC 230 also calls it the reconciliation method
- Deferred revenueConsideration received, or unconditionally due, before the goods or services are transferred — a liability until the performance obligation is satisfied. ASC 606 calls it a contract liability
In the founder glossary
This lesson’s ideas, explained for the founder running the company. Each has an entry in the founder glossary.
See also
- Statement semanticsThe P&L, balance sheet and cash flow statement are three views of one set of facts, and they tie to each other. This page covers how each one is structured and what the statement components enforce as a result.
- Metrics & analysisMetrics & analysis — specs for 13 React components: MetricDefinition, NonGaapReconciliation, MrrBridge, BudgetVsActual and 9 more.
- Journal entry for deferred revenueWhen an annual contract is invoiced up front, debit Accounts receivable and credit Deferred revenue. As each month of service is delivered, debit Deferred revenue and credit Revenue for that month's share.
- Journal entry for a customer depositWhen a customer pays a deposit, debit Cash and credit Customer deposits. On delivery, debit Customer deposits for the deposit, debit Accounts receivable for the balance, and credit Revenue for the full price.
- Journal entry for a sale on accountFor a sale on credit, debit Accounts receivable and credit Revenue for the price; under a perpetual inventory system also debit Cost of goods sold and credit Inventory for what the goods cost. When the customer pays, debit Cash and credit Accounts receivable.
- Journal entry for an inventory purchaseWhen inventory is bought on credit under a perpetual system, debit Inventory and credit Accounts payable. If an early-payment discount is taken, debit Accounts payable for the full bill, credit Cash for what is paid and credit Inventory for the discount.
- Working capital calculatorWorking capital is a liquidity and working-capital metric, calculated as Current assets − Current liabilities.
- DSO calculatorDSO is a liquidity and working-capital metric, calculated as (Ending AR ÷ Credit sales for the period) × Days in the period.
- DPO calculatorDPO is a liquidity and working-capital metric, calculated as (Ending AP ÷ COGS for the period) × Days in the period.
- Free cash flow calculatorFree cash flow is a cash and runway metric, calculated as Operating cash flow − Capital expenditures.
- Balance sheet vs income statementThe balance sheet shows what a company owns and owes on one date. The income statement shows what it earned and spent over a period, and its bottom line feeds equity on the balance sheet.
- Retained earnings vs net incomeNet income is one period's profit. Retained earnings is every period's net income since the company began, less every dividend, carried as a balance in equity.
- Direct method vs indirect methodThe direct method lists operating cash receipts and payments; the indirect method starts from net income and adjusts for non-cash items and working-capital changes. Both arrive at the same operating cash flow.
- Cash flow statement explained: why profit isn’t cashHow the cash flow statement starts at net income, adds back non-cash costs and working capital, splits three activities and ties to the balance sheet.
- Balance sheet explained for startupsAssets equal liabilities plus equity. What each startup line means, from deferred revenue to the SAFE and the accumulated deficit, and why it must balance.
- How to read an income statement (P&L)Revenue, cost of revenue, gross margin, operating expenses and net income, read line by line, on accrual basis, with the mistakes founders make most.
- DriverModelThe inputs a forecast is built from, and what they produce.
- ForecastTableProjections dashed and labeled everywhere.
- ProfitAndLossP&L with period comparison and variance.
- BalanceSheetAssets / liabilities / equity, with the balance check.
- CashFlowStatementOperating / investing / financing.
- ScenarioCompareScenarios side by side, all measured against the base.