Small Business 13-Week Cash Flow Forecaster

---
name: small-business-13-week-cash-flow-forecaster
description: Builds a 13-week cash flow forecast for a small business or startup from a CSV of receipts and payments - weekly, biweekly, monthly, quarterly and one-off items, invoices on net terms with customer lateness, probability-weighted deals - with a base and a stress case. Finds the low point, the week cash drops below the buffer, the gap, deferrable payments, key invoices and runway. Includes an offline stdlib Python forecaster with --self-test.
---

# Small Business 13-Week Cash Flow Forecaster

You help an owner, founder or bookkeeper see the next quarter of cash week by week: what comes in, what goes out, where the balance bottoms out, and what to do before it gets there. Profit and loss says whether the business makes money; the 13-week forecast says whether it can pay salaries on the 1st. You keep the inputs as a CSV anyone can edit, count invoices when customers really pay (not when they are due), weight uncertain deals, run a stress case next to the base case, and turn the low point into a short list of actions.

## Files in this skill

- `scripts/cashflow13.py` - reads the CSV, expands every schedule into dated payments in the horizon, applies customer lateness and probabilities, rolls the balance week by week in cents for a base and a stress case, and reports the low point, the first week below the buffer, the gap, credit line cover, the recurring run-rate and runway, flexible payments before the low point, the invoices that matter, customer concentration and one week's detail (Python 3.8+ standard library only)
- `references/forecast-method.md` - the CSV format, schedules, timing rules, the base and stress cases, and how to keep the forecast honest week after week
- `references/cash-levers.md` - what to do about a gap: collect, defer, cut, finance, in order of cost and speed
- `templates/cash-flow-brief.md` - the one-page brief to hand back
- `examples/studio-cashflow.csv` - a 5-person design studio: retainers, invoices on 30/45-day terms, an overdue invoice, an 80% milestone, a 40% pitch, biweekly salaries, VAT, tax prepayment, a year-end bonus and a 20,000 EUR credit line
- `examples/studio-forecast.md` - the real output of the forecaster on that file
- `examples/cafe-winter.csv` - a cafe with weekly takings and suppliers, a January dip, quarter-day rent and a VAT bill in the same month

## Workflow

### 1. Collect the inputs
Ask for: cash in the bank today (all accounts the business can use, minus cheques not yet cleared), the minimum balance the owner wants to keep (one payroll plus a month of fixed costs is a common floor), any undrawn credit line, and the start Monday. Then list every receipt and payment for the next 13 weeks: recurring income (retainers, subscriptions, takings), open invoices with invoice date and terms, expected new work with an honest probability, payroll and payroll taxes, rent, loans, suppliers, software, tax and VAT dates, annual bills, planned purchases and bonuses. Ask how late customers usually pay and which payments could move (`flex=yes`). Use the bank statement and the accounting system's aged receivables/payables lists, not memory.

### 2. Run the forecaster
```
python3 scripts/cashflow13.py examples/studio-cashflow.csv
python3 scripts/cashflow13.py forecast.csv --opening 41250 --min 15000
python3 scripts/cashflow13.py forecast.csv --stress-cut 30 --stress-delay 21 --week 9
python3 scripts/cashflow13.py forecast.csv --json
python3 scripts/cashflow13.py --self-test
```
Exit 0 = both cases stay at or above the buffer, 1 = cash drops below the buffer (or below zero) in either case, 2 = the CSV has an error (the message names the line). Without a shell, build the same table by hand: one row per week, receipts, payments, net, closing balance; then repeat with the stress assumptions.

### 3. Read the result
- Look at the low point first, in both cases: the week, the amount, and the gap to the buffer.
- Check what drives it with `--week N`: often a cluster (salaries + rent on the 1st, VAT, a quarter-day rent, a bonus) meeting a gap in receipts.
- Stress case: if it goes below zero, is the credit line enough, and for how long?
- Concentration: one customer above about 30% of receipts makes their payment date the forecast.
- Run-rate: negative means the business relies on one-off income; say how many weeks the closing cash lasts without it.

### 4. Turn it into actions
Use `references/cash-levers.md`: collect first (chase overdue invoices, invoice milestones on the day they are reached, ask for deposits), then time payments (defer or split flexible items, agree a payment plan for tax before the due date, lease instead of buy), then cut, and only then finance (draw the credit line for a known gap with a known repayment week). Re-run the forecast with each change so the owner sees the new low point.

### 5. Deliver and roll forward
Fill `templates/cash-flow-brief.md`: verdict, low point in both cases, the weekly table, the drivers, the actions with amounts and owners, and the assumptions. Agree a weekly update: replace the week just ended with actual cash, add week 14, and note forecast vs actual for the biggest lines so the probabilities get better.

## Example result
On `examples/studio-cashflow.csv` the studio starts with 38,500 EUR. The base case dips to 13,160 EUR in week 9 (28 Dec), 1,840 below the 15,000 buffer, when salaries, rent, the illustrator and the loan land before the Hafen Bank and Atlas payments. In the stress case (pitch dropped, invoices two weeks later, retainers -20%) cash goes below zero in week 7 and ends week 13 at -16,590 EUR; the 20,000 credit line covers that with 3,410 to spare but not the buffer. Levers before the low point: the 7,000 bonus, 4,800 of laptops and the illustrator (20,200 flexible in total), plus collecting the 18,600 Hafen Bank invoice on time. Nordwind brings 36% of expected receipts. The cafe example shows a different pattern: VAT and quarter-day rent in December meet a January dip, and the base case stays below its 4,000 buffer from week 8.

## Rules

- Forecast cash, not profit: dates money moves, including VAT and payroll taxes, excluding depreciation and accruals.
- Never invent amounts, dates or probabilities; ask, or list them as assumptions in the brief.
- Count invoices when customers really pay, with their usual lateness; overdue invoices go in week 1 at a probability the owner believes, or out.
- Keep base and stress side by side; do not present only the optimistic case.
- Recommend financing only for a specific, temporary gap with a repayment week in the forecast.
- This is planning support, not tax, legal or lending advice; suggest an accountant for tax payment plans and loan terms.
FILE:references/forecast-method.md
# Forecast method

## CSV format
```
# business: Lumen Design Studio
# currency: EUR
# start: 2026-11-02          first Monday of week 1
# weeks: 13
# opening_balance: 38500     usable cash today
# min_balance: 15000         buffer you do not want to go below
# ar_delay_days: 10          customers pay this many days after the due date on average
# credit_line: 20000         undrawn facility (optional)
item,kind,amount,schedule,start,end,probability,flex,notes
```
- `kind`: `in` (receipt) or `out` (payment). `amount`: positive, per occurrence, gross of VAT if VAT is charged/paid.
- Quote any text that contains a comma (`"Adobe, Figma"`); unquoted extra fields are moved into notes with a warning.
- Name customer receipts `<what> - <customer>` (e.g. `INV-1042 app design sprint - Hafen Bank`) so the concentration check can group them.

## Schedules
| Schedule | Meaning | Example |
|---|---|---|
| `once:2026-11-20` or `2026-11-20` | one payment on that date | equipment, tax bill |
| `weekly:fri` | every Friday in the horizon | wages, takings |
| `biweekly:2026-11-06` | every 14 days from the anchor (earlier anchors are fine) | salaries every second Friday |
| `monthly:15`, `monthly:last` | that day each month; 29-31 clamp to the month end | rent, loan, payroll taxes |
| `quarterly:2026-12-25` | every 3 months from the anchor | quarter-day rent, quarterly VAT |
| `yearly:2026-01-15` | once a year on that date | insurance, licences |
| `net:30` with `start` = invoice date | due = invoice date + 30 days, plus `ar_delay_days` for receipts | open invoices, supplier bills |

`start` and `end` limit recurring items (a contract that ends, a price change: two lines with different dates).

## Timing rules
- Weeks run Monday to Sunday from `start`; a Saturday payment lands in the same week, which is how banks clear most weekend card income anyway.
- Receipts on net terms arrive `ar_delay_days` after the due date. Measure lateness from the last 6-12 months (average days between due date and payment).
- Anything dated before week 1 (an overdue invoice, an unpaid bill) is counted in week 1, with a warning. Give overdue invoices a realistic probability or leave them out.
- Items after the horizon are counted and reported, not shown.

## Base and stress cases
- Base: every amount x its probability (a 40% pitch worth 15,000 counts 6,000). Fine for totals, misleading for timing of a single big deal, so the stress case drops those.
- Stress (defaults): receipts below 90% probability dropped, invoice receipts `--stress-delay` 14 days later, recurring receipts cut by `--stress-cut` 20%. Payments unchanged.
- Choose stress settings that match the business: a cafe in January might use -25% takings; an agency with one big client should also test that client paying a month late (copy the CSV and move that line later).

## Keeping it honest
- Start from the bank balance, not the accounting balance.
- Include VAT/sales tax both ways and the dates it is paid to the authority; payroll taxes on their own dates.
- Update weekly: actuals in, one new week added, probabilities revised. Track forecast vs actual for the five biggest lines; persistent misses mean a wrong assumption (lateness, seasonality).
- Recurring run-rate = recurring receipts minus recurring payments per week; negative means the business lives on one-off income.
- The forecast is only as good as the inputs; list every assumption in the brief.
FILE:references/cash-levers.md
# Cash levers, in the order to try them

## 1. Collect faster (cheapest)
- Chase overdue invoices now, by phone, with a named contact and a promised date; offer a payment plan rather than waiting.
- Invoice the day a milestone is reached; invoice retainers in advance on the 1st, not in arrears.
- Ask for deposits (30-50%) on new projects and staged payments on long ones.
- Shorter terms on new contracts (14 days), card or direct debit for small clients, a small early-payment discount only if the margin allows it.
- Large customers often pay on fixed runs (e.g. the 25th): learn the run date and invoice before it.

## 2. Time payments
- Defer or split flexible purchases (equipment, bonuses, marketing); lease or rent instead of buying.
- Ask suppliers for longer terms before the bill is due, not after.
- Tax: most tax authorities offer payment plans if asked before the due date; ask an accountant.
- Move payroll-adjacent extras (bonuses, training) to after the low point; never delay salaries or payroll taxes as a plan.

## 3. Cut
- Unused software seats and subscriptions, overlapping tools, discretionary travel.
- Freelancers on fixed monthly fees -> project billing.
- Renegotiate rent or service contracts at renewal.

## 4. Finance (for a known, temporary gap)
- Draw the credit line/overdraft for the gap weeks only, with the repayment week visible in the forecast.
- Invoice financing/factoring for large slow customers (costs 1-3% per month; check the contract).
- Owner loan or equity for a structural gap (negative recurring run-rate): financing only buys time; fix the run-rate.

## How to present levers
| Lever | Amount | Week it helps | Effort / cost | Owner |
|---|---|---|---|---|
| Collect INV-1038 K

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