Seasonal Business Cashflow Calculator NZ 2026

Reviewed 7 August 2026.

Quick answer Five high season months at $12,000 and seven low months at $2,500, against $4,500 of monthly costs, makes $23,500.00 across the year. But the low season loses $14,000.00, and starting the year with the low season takes cash down to -$9,500.00 in month 7. To get through without borrowing you would need to start with $17,500.00.
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A seasonal business can be comfortably profitable across a year and still run out of money in the middle of it. Profit is an annual measure and cash is a monthly experience, and for anyone whose income arrives in a concentrated few months those two things come apart badly. The costs do not take a season off. Rent, insurance, vehicle payments, and your own living expenses continue at the same rate through the quiet months, funded by whatever the busy months left behind. Whether that works depends on three things: how deep the low season is, how long it lasts, and crucially which season you are in when the year starts. This calculator runs the year month by month rather than annually, tracks the cash balance as it moves, and reports the lowest point it reaches and when. That lowest point, not the annual profit, is the number that determines whether the business survives its own season.

Lowest cash point
-$9,500.00
reached in month 7
Opening cash needed
$17,500.00
to never go below zero
Surplus for the year
$23,500.00
before $15,500.00 of tax reserved

The two seasons

High season income$60,000.00
High season costs$22,500.00
High season surplus$37,500.00
Low season income$17,500.00
Low season costs$31,500.00
Low season deficit-$14,000.00
Annual income$77,500.00
Annual costs$54,000.00
Annual surplus before tax$23,500.00
Tax reserved across the year$15,500.00
Does the high season cover the low?Yes
Months the balance is negative5

Month by month

Negative months are shaded and the lowest point is highlighted. Tax reserved leaves the operating balance as it is set aside.

MonthSeasonIncomeOutTax reservedBalance
This is a projection. It assumes every high month is the same as every other and the same for low months, which smooths over the shoulder periods most seasonal businesses actually have. It also assumes income is received in the month it is earned, so if you invoice on terms the real cash arrives later than shown and the low point is deeper. Provisional tax instalments are not modelled as separate events, since their dates depend on your balance date and method.

The order of the seasons decides the answer

Two businesses with identical annual figures can be in completely different positions depending on where the year starts. Beginning with the high season means building a balance before the costs of the quiet months have to be met, and the low point of the year is simply the opening balance. Beginning with the low season means funding months of deficit before any surplus arrives, and the low point can be tens of thousands below zero. Nothing about the profitability of the business has changed between those two cases. This is why an annual budget is not a cashflow plan, and why the season your balance date falls in matters more than most people expect.

Tax reserved is not available to cover the low season

The temptation in a seasonal business is enormous: the high season generates a large balance, the low season is expensive, and the tax on the high season is not due for months. Spending the reserve to get through the quiet period works exactly once, and then the bill arrives during the next low season when there is even less to pay it with. This calculator deliberately takes the tax reserve out of the operating balance as it is set aside, so the balance shown is money you can actually use. If that line goes negative, borrowing or a shorter low season are the honest answers, not the tax account.

What to do with a deep low point

There are only four levers and it is worth knowing which one you are pulling. You can start the year with more cash, which means saving through the previous high season. You can shorten the deficit by finding any income at all for the quiet months, and note that the calculation is very sensitive to this: a small amount of off-season income repeated over several months closes a surprising share of the gap. You can cut fixed costs, which is the only lever that helps in every month of the year. Or you can arrange an overdraft before you need it, which costs money but is far cheaper than arranging one in the month you run out.

Worked example

A seasonal operator has 5 high season months taking $12,000.00 each and 7 low months taking $2,500.00, so annual income is $77,500.00. Fixed costs run at $4,500.00 a month, or $54,000.00 a year, leaving an annual surplus of $23,500.00 before tax. On those numbers the business is clearly viable.

The high season produces a surplus of $37,500.00 and the low season a deficit of $14,000.00, so the year covers itself comfortably. But starting with the low season, and reserving 20% of income for tax as it arrives, the balance falls through every quiet month and reaches -$9,500.00 in month 7, having started at $8,000.00. Getting through without borrowing would take $17,500.00 of opening cash.

How this is calculated

The year is run as twelve individual months rather than as two seasons. Each month adds its income, subtracts the fixed costs, and subtracts the tax reserved on that month's income, then carries the balance forward. Which months are high and which are low is set by the season you choose to start with. The lowest cash point is the minimum balance across all twelve months, and the opening cash needed is your current opening balance plus whatever that minimum falls below zero. Seasonal totals are the per-month figures multiplied by the number of months in each season.

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Frequently asked questions

Why does the order of the seasons matter for cashflow?

Because a business that earns before it spends is in a completely different position from one that spends before it earns, even when the annual total is identical. Starting the year with the low season means funding months of deficit before any surplus arrives, which is where seasonal businesses fail despite being profitable across the year.

My seasonal business is profitable, so why do I run out of cash?

Profit is measured across the year, cash is experienced month by month. A business with a healthy annual surplus can still hit zero in the middle of a long low season, because the surplus arrives later than the costs. Profitability tells you the year works; the lowest cash point tells you whether you survive to see it.

How much cash should a seasonal business start the year with?

Enough to cover the deepest point of the year plus a margin. This calculator works out the deepest point directly from your own figures, which is a better answer than any rule of thumb, because it depends entirely on how long your low season is and how much still comes in during it.

Should I reserve tax during the high season?

Yes, and seasonal businesses are the case where it matters most. The high season generates the income the tax is charged on, but the bill often falls due during or after the low season, when the money has been spent covering the quiet months. Reserving as income arrives is the only reliable way through this.

Does provisional tax make seasonal cashflow worse?

It can. Provisional tax instalments fall on fixed dates that have nothing to do with your trading pattern, so an instalment can land squarely in your quietest month. If that is your situation, the ratio method or AIM may fit your cashflow better than the standard method.