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How to budget when your income changes every month

A budget built on your average month fails on your worst one. The fix is to budget for the floor, not the forecast - and let good months fill the tank instead of raising the ceiling.

The short answer

Set it up in one sitting

  1. List the last twelve months of income. Circle the lowest. If you have less than a year of history, use a number you are sure you can beat in a bad month.
  2. List your fixed costs: rent, utilities, food floor, insurance, taxes. This is the baseline - the monthly number the business of you must always pay.
  3. Open a second account. All income lands here; on the 1st, move exactly the baseline to your main account and nothing more.
  4. Set aside tax the day money arrives - a fixed percent into a separate pot, before anything else. Tax is a cost of the invoice, not of April.
  5. Write the ceiling on the budget page. Anything above it in a month is not spending money; it is smoothing-account money by definition.

Why averages lie

A freelancer earning an average of $3,000 a month and a salaried employee earning $3,000 a month live in different financial universes. The employee can spend $3,000; the freelancer has months of $800 and months of $6,000, and the $800 months arrive without an appointment. Averaging hides the shape of the income - and the shape is what hurts. Budgets built on averages break in the first valley and get abandoned, which is worse than never starting. The floor-based budget survives every month by design, because it only ever promises the worst case.

Mistakes that break it

The free tool for this

The 50 / 30 / 20 split, on your own numbers - The 50 / 30 / 20 split, on your own numbers. It runs in the page, asks for your own numbers, and sends nothing anywhere.

If you would rather not build it yourself

Money Map is built for exactly this: one page that shows the floor, the fixed costs and the smoothing balance together, so the first-of-month check is a glance, not an evening. Money Map is $14. See it on the shop, and there is a plain page about it here: what it holds.

Questions people actually ask

How many months should the smoothing account hold?

Three baseline months is the working minimum, six is comfortable. Below three, any surprise becomes debt; above six you can start thinking about investing the overflow instead of just surviving it.

What if my income is zero this month?

That is exactly what the smoothing account is for - the baseline still gets paid from it. If it cannot cover that, the honest next step is cutting the baseline or raising income, not borrowing against a forecast.

Should I use the envelope method with irregular income?

Envelopes work for spending, not for income swings. Keep the two-account split for income smoothing, and if you like envelopes, use them inside the baseline for variable categories like food.

Read next

How to make a household budget you will still be keeping in February, How to work out your net worth on one page, without the jargon.

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