How accurate is a 13-week cash forecast?

Weeks 1-4 should be highly accurate (within 5%) because most payments and receipts are already committed. Weeks 5-8 are moderately accurate (within 10-15%). Weeks 9-13 are directional. Update weekly to maintain accuracy.

Should I use direct or indirect method?

For a 13-week forecast, always use the direct method (actual cash in and cash out). The indirect method (starting from net income) is better for longer-term cash flow statements. The direct method gives you the operational visibility needed for short-term cash management.

How do I forecast customer receipts?

Start with your accounts receivable aging report. Apply historical collection rates by customer segment and payment terms. For known large invoices, schedule them individually. For the remainder, use a weighted average based on your DSO (days sales outstanding).

What is a good minimum cash threshold?

A common rule of thumb is 2-4 weeks of operating expenses. For the company in this example, that is roughly £40-80k. The £50k threshold gives about 2.5 weeks of runway before critical decisions would be needed.

Example

13-Week Cash Flow Forecast Example

A 40-person e-commerce company in Leeds with £2.8M revenue. The business is profitable but cash-tight due to inventory purchasing cycles. The finance team runs a weekly 13-week cash forecast to ensure the company never drops below its £50k minimum cash threshold.

Example data

Financial model

Cash Flow

Wk 1

Wk 2

Wk 3

Wk 4

Wk 5

Opening Balance

£185k

£142k

£168k

£131k

£156k

Customer Receipts

£62k

£78k

£45k

£85k

£58k

Other Income

£3k

£1k

£2k

£1k

£3k

Supplier Payments

(£68k)

(£28k)

(£52k)

(£30k)

(£65k)

Payroll

(£25k)

Other Payments

(£40k)

(£32k)

(£6k)

(£12k)

Closing Balance

£142k

£168k

£131k

£156k

£140k

Customer Receipts

Receipt timing is lumpy because key retail customers pay on 30-day terms. Week 4 shows a large receipt from a quarterly settlement with the largest customer.

Payroll

Payroll runs fortnightly, hitting in weeks 2 and 4. This is the most predictable outflow and anchors the cash forecast.

Closing Balance

The lowest projected balance is £131k in week 3, comfortably above the £50k threshold. The forecast gives 13 weeks of advance warning if that changes.

Formulas

Key formulas

fxClosing Balance = Opening + Total Receipts - Total Payments

The fundamental cash equation. Each week's closing balance becomes the next week's opening balance, creating a chain of cash visibility.

fxCustomer Receipts = Invoiced Revenue * Collection Rate by Week

Receipts are modelled based on invoice aging. Typically 40% collected within 7 days, 35% at 14 days, 20% at 30 days, and 5% at 60+ days.

fxMinimum Cash Alert = IF(Closing < £50k, "ALERT", "OK")

A conditional check ensures the team is alerted if projected cash drops below the £50k minimum threshold at any point in the 13-week window.

Analysis

What makes this example good

Weekly granularity catches short-term cash pinch points that monthly forecasts miss

Opening/closing chain ensures mathematical integrity across the forecast

Separate lines for receipts and payments by category aid in variance analysis

Minimum cash threshold provides an early warning system

Payroll timing explicitly modelled as the most predictable major outflow

Customisation

How to adapt for your business

Add a VAT payments row if quarterly VAT is material to your cash position

Include a credit facility drawdown line if you have a revolving credit facility

Break customer receipts into segments (retail, wholesale, online) for better forecasting

Add a "worst case" scenario row that delays all receipts by 7 days

Extend to 26 weeks if your business has longer cash conversion cycles

Common variations

--Daily cash forecast for the first 4 weeks, weekly thereafter
--13-week forecast with separate tabs for each major customer
--Cash flow forecast integrated with P&L forecast for full visibility
--Multi-currency cash forecast for businesses with international operations

Keep exploring

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FAQ

Frequently asked questions

Thirteen weeks equals one quarter. It provides enough forward visibility to manage working capital and plan for large payments (e.g., quarterly VAT, rent deposits) while being short enough that the forecast remains reasonably accurate.

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