What Are Budget Rules? And What a Budget Spreadsheet Leaves Out

Budget rules are decisions you make once, in advance, about what gets paid first, how much each category can take, and what happens when a month comes up short. A budget spreadsheet records where the money went. The rules turn that record into a plan, because they settle the question before the pressure arrives. This note covers what a rule does, why a single percentage rule fits some pay patterns better than others, and how to read a budget that does not add up.

What a budget spreadsheet records, and what it leaves out

A spreadsheet is a document. It holds numbers and accepts whatever you type. If you overspend a category, it updates the total without comment, because nothing in it has been told what to enforce.

A budget spreadsheet is, on its own, a record. A record answers “what did I spend?” A budget answers “what will I spend, and in what order?” ASIC’s Moneysmart site treats these as two tasks. Its budgeting section lists one page to “see where your money goes” and another to set up “a simple plan for your income and expenses”, and its tracking page suggests making a budget once you feel confident you know what you spend.

How to start budgeting covers writing down what comes in and what goes out. This note starts after that, when the numbers are on the page and the next question is what governs them.

What a budget rule does

A rule is a decision made once, in advance. Does a new expense come out of groceries or out of discretionary spending? Does saving come first or last? Without a rule you answer those questions fresh every month, usually when you are short of time or money. With one, the answer already exists, and the same situation gets the same treatment each time.

Two orders of operation can look identical on screen. In one, you spend and record, then react to the totals. In the other, the split is decided before the month starts and the spending happens inside it. The cells are the same. What differs is whether the decision came before the money moved or after.

Moneysmart’s steps for making a budget include setting a savings goal and reviewing when things change, and its tracking page suggests setting “a weekly or monthly limit” for wants. A goal and a limit are both rules in the sense used here: a line drawn ahead of time.

One commonly cited example, which Moneysmart does not publish, is the 50/30/20 method. It splits after-tax income into 50 per cent for needs, 30 per cent for wants and 20 per cent for saving or paying down debt. It is described here to show how a split decided in advance works, and it is not a recommendation. What makes it a rule is the timing. The split exists before the money arrives, and any structure that works in that order does the same job, whatever its percentages.

When a rule comes with its reason attached, what is a money principle calls it a principle. That note covers the difference. This one stays with the rules.

Where a percentage rule meets pay that moves

A percentage rule takes a share of whatever income arrives, so it gives steady dollar figures only when the income is steady. When pay moves, the dollar amounts move with it, and many costs do not.

Take invented numbers. Say take-home pay is $4,000 in one month and $2,500 in the next, and rent is $1,600 in both. Fifty per cent for needs is $2,000 in the first month and $1,250 in the second. Rent is 40 per cent of the first month’s pay and 64 per cent of the second, so in the lean month it sits above the needs line by itself. The percentage and the rent each do what they say. They do not fit together in a month like that.

Pay moves for many reasons, and care is one.

The ABS Survey of Disability, Ageing and Carers found that in 2022, 12.8 per cent of all females were carers, against 11.1 per cent of all males, where a carer is someone who provides informal help or supervision to a person with disability or to someone aged 65 or over. Two-thirds (67.7 per cent) of primary carers were female.

The ABS says that “undertaking a caring role can affect a person’s capacity to work and earn an income”, and among primary carers aged 15 to 64 who gave more than 40 hours of care a week, 45.4 per cent were employed, against 71.6 per cent of those who gave less than 20 hours. Casual work, part-time hours and career breaks can move income too.

Shared money adds questions that no generic percentage answers. Whose income is the base figure? Who carries which category? What happens when contributions are unequal and the costs are shared? A budget for two needs those answered in words before the numbers mean much.

Why the usual rules were not written with this in mind

A rule that assumes one steady income and an unbroken working life describes a pattern that was not equally open to everyone, and the history is recent. Until 1966 a married woman could not hold a permanent job in the Commonwealth Public Service. The Public Service Act (No. 2) 1966 removed that bar, and it took effect in November 1966. The states had their own marriage bars and removed them on their own timelines.

In August 1987, five years before the Superannuation Guarantee began, the ABS found that 26.0 per cent of female employees were covered by an employer super scheme, against 49.9 per cent of male employees. Sex discrimination in lending did not become unlawful across the whole of Australia until the Sex Discrimination Act 1984 commenced, on 1 August 1984.

The longer story is in when could women open a bank account in Australia and why women were never taught about money. The pattern reaches the other end of a working life too. Super Members Council analysis of ATO tax data puts the median super balance of women aged 60 to 64 at $174,700 against $236,100 for men in 2023-24, a gap of $61,400, or 26 per cent. Why women retire with less super covers how that gap builds.

What a written set of rules answers

A set of rules does not need to be long. It needs to answer a handful of questions in writing, in the same document as the numbers, so it can be read and changed. A rule held in memory cannot be checked by anyone, including you.

What does this budget protect? Some costs are hard to move at short notice, rent among them, and a rule can put them first. Naming what the budget protects tells you which costs those are.

What kind of income feeds it? A fortnightly payslip and an irregular invoice are different inputs, and a rule that suits one may not suit the other. Moneysmart’s budget steps say that if income varies from week to week, you work out an average amount. Its casual income page describes other approaches: saving for lower-income weeks, asking service providers whether you can pay fortnightly or monthly (“bill smoothing”), and keeping separate accounts for everyday spending, regular bills and savings.

Which costs arrive once a year? Moneysmart lists car repairs and services, annual bills and pet costs among the irregular costs a budget includes, and its tracking page suggests highlighting bills that come up quarterly or yearly. A budget that lists only monthly costs has nowhere to put these, so a bill that was always going to land once a year turns up in a month with no room for it.

Who owns what, when the money is shared? A rule can say who covers which category, and what happens when one income is late or lower. Where that is left unsaid, it gets settled the first time it matters, usually in a hurry.

When the numbers do not line up

A shortfall is information about the rules before it is anything else. A budget built six months ago, or in a different job, was built for a different month. When it stops adding up, three things can change in principle: how the money is split, the amounts in each category, or the income itself. A spreadsheet cannot choose between them. Someone has to decide, and the rules are where that decision is recorded.

Moneysmart’s last budget step is to review and adjust, updating the budget as circumstances change, and it says checking the budget each month keeps it accurate. A review on a set date, rather than only in a crisis, means the rules are looked at while there is time to think.

Sometimes the rules are sound and the income falls short of the costs. That is a gap between income and costs, and no ordering of categories closes it. Free financial counselling exists for that, and the National Debt Helpline, on 1800 007 007, is independent and confidential.

If you would like a free tool for the adding, there is a budget calculator on the site.