How zero-based budgeting works, with a worked month

Zero-based budgeting means that before the month starts, every dollar of the month's income is assigned to a category, so that income minus everything planned, spending, saving, and debt payments, equals zero. Zero is the amount left to assign, not the amount left in the account; savings and debt payments are assignments like any other. When a category runs over during the month, money is moved to it from another category rather than found, and at month end anything unspent is assigned again. The method suits people who want a decision behind every dollar and wears out people who want a budget they can set and leave.

What zero-based actually means

The rule is a single equation: income for the month, minus every planned amount, equals zero. Rent, groceries, and the phone bill are planned amounts, and so are the emergency fund transfer, the extra loan payment, and the money set aside for car repairs. A dollar not assigned to anything is the one dollar the method forbids, because an unassigned dollar sits in checking reading as available and is spent without a decision.

Zero does not mean the account hits zero. A household assigning $300 to savings and $250 to extra debt payments has $550 leaving the account for places it chose, and the checking balance ends the month wherever the timing of bills leaves it. The zero is on the plan.

Build the month

1. Write down the month's income, the take-home amount that will actually arrive. If pay is irregular, use the money already in hand rather than the money expected; see How to budget on irregular or variable income.
2. Assign the fixed bills first, at their exact amounts, since they are not decisions.
3. Assign the goals next: the emergency fund, extra debt payments, and the monthly shares of annual bills. Putting them before the variable categories is what makes them happen.
4. Assign the variable categories from three months of real spending, rounded.
5. Assign the last dollar. If income exceeds the assignments, give the remainder to a goal. If the assignments exceed income, cut categories until they fit; the method does not allow a plan that spends more than arrives.

A worked month

Take-home income is $4,200.

The savings and debt lines, $650 between them, are assigned before dining and shopping got their amounts, which is the reason they exist at all. Had the variable categories been filled in first, at last month's actual figures, the month would have arrived at zero with nothing set aside, and the plan would have been a description rather than a decision.

When a category runs over, move money, not the rule

On the 20th, groceries reach $590 against $550. The method's answer is to move $40 into groceries from a category that still has room, dining out at $250 with $120 spent, and to write the move down. Dining out is now $210 for the month and groceries $590; the total is still $4,200 and the plan is still at zero. Nothing was borrowed from next month and nothing came from savings unless savings was the category chosen, on purpose.

Moving money is the method's defining move, and it is also its cost. A household that moves money four times a month is doing the work the method asks for. One that finds the moves tedious will stop recording them by the third month, at which point the plan and the spending have parted and the budget is decorative.

Month end: unspent money gets a job too

At the end of the month, entertainment has $30 unspent and shopping $45. In a zero-based month those dollars are not carried forward automatically and not left in checking; they are assigned again, the same way income is. The usual choices are the emergency fund, the next extra debt payment, or the following month's set-aside for a lumpy category. The point is that the $75 gets a decision before it becomes available. See What to do with the money you didn't spend this month for which categories should carry a balance and which should be swept.

Who it suits, and who it wears out

Zero-based budgeting suits people who want to know where every dollar went and are willing to spend twenty minutes at the start of the month and a few minutes a week keeping the plan true. It is strongest when income is tight, because forcing the assignments to fit is what surfaces the trade-off between dining out and the loan payment before the month makes it silently.

It wears out people who want a budget to run without them. The method has no autopilot: an unassigned dollar, an unrecorded move, or a skipped month-end sweep breaks the equation, and the equation is the whole method. For those households a category budget with a few carried balances asks for less and holds longer; see Envelope vs. zero-based vs. 50/30/20 budgeting for the comparison.

Common mistakes

• Assigning the variable categories before the goals. The goals get what is left, which is nothing.
• Reading zero as an empty account. Zero is the plan's remainder; the account carries whatever the bills' timing leaves.
• Covering an overage from next month. Next month's income is not this month's to assign. Move money within the month or accept the overage on the record.
• Leaving unspent money in checking at month end. It is unassigned by definition, and unassigned money is what the method exists to prevent.
• Planning on expected income when pay is irregular. Assign money that has arrived. A plan built on a paycheck that comes in smaller is over before it starts.
• Keeping thirty categories. More lines mean more moves. Ten to fifteen is enough to make every dollar's job clear.

Common questions

Is zero-based budgeting the same as the envelope system? They overlap. Envelopes cap each category at its amount; zero-based adds the rule that the amounts must use up the income exactly, and that money moves between envelopes rather than appearing from outside. Most envelope budgets are zero-based in practice, and most zero-based budgets use categories as envelopes.

What if my income is irregular? Assign only the money you already have. A month starts with what is in the account, gets assigned to zero, and when more arrives it is assigned then. The method works well with irregular pay for exactly this reason: it never plans on money that has not landed.

How long does it take each month? About twenty minutes at the start to set the assignments, and a few minutes a week to record moves and check the categories. Months two and three are faster than month one, because the fixed lines and most of the variable ones repeat.

Do savings and debt payments really count as assignments? Yes, and it is the most important feature of the method. They are given their amounts before the variable categories, at the same standing as rent, which is why a zero-based budget builds savings where a "spend less than you earn" budget does not.

How Zypper handles this

Zypper gives you the equation without forcing it. Left to budget, above the category list on the budget page, is your expected income minus everything you have budgeted for spending, with every amount standardized to a monthly figure: at zero the plan is zero-based, and a negative figure means you have planned to spend more than you expect to earn. Nothing has to add to zero and nothing moves money between categories, so the mid-month move is made by changing the two amounts for this month only, with Apply to [month] forward unchecked, and a category's Activity tab records each change with its date. Categories that should carry their unspent balance, the set-asides for car repairs and annual bills, use Roll over unspent budget, so the month-end sweep happens for those rows on its own. See Creating your budget and Rolling over unspent budget for the details, or get started with Zypper to give your own month its jobs.