Plan on a low month, not an average one
Look at your income over the last 12 months and find the lowest typical month. Leave out a one-off disaster month, but don't pick a good one. If you are new to irregular work and don't have 12 months of history yet, use a cautious estimate and update it as your records grow.
Build your budget as if every month paid that amount. Essentials must fit inside it. Anything you earn above it is extra, not something your rent depends on.
Use a buffer account
Open a separate account and send all your income there first, whatever the month brings. Your everyday account is then filled from the buffer, never directly from clients or employers.
Good months fill the buffer and slow months draw it down. The salary you pay yourself still goes out in a month with no income at all – that is what the buffer is there for. If no tax is taken from your income automatically, keep tax money apart from both accounts – how much to set aside depends on your country.
Pay yourself a fixed salary
Once the buffer holds a little money, move the same amount to your everyday account on the same day each month, ideally a few days before rent and other big bills are due. From your everyday account's point of view, your income is now regular, so a normal budget like the one in your first budget works again.
A worked example
Over the past year your monthly income ranged from €1,400 to €2,800, with an average of €2,100. You set your salary at €1,400, the lowest typical month, and build your budget on that.
In a €2,800 month, €1,400 goes to your salary and €1,400 stays in the buffer (2,800 − 1,400 = 1,400). In a €1,400 month, the buffer doesn't change. Once the buffer holds two months of salary, €2,800 (1,400 × 2), a slow month no longer causes stress.
When to raise your salary
Raise your fixed salary only when the buffer has stayed above its target for several months. Raise it in small steps, and if the buffer starts shrinking, go back down.
Money that keeps piling up above the target can move to your emergency fund or other goals. For irregular earners, a bigger emergency fund is a sensible aim, which the next module explains.