Budget rollover

By default a monthly budget starts fresh on the first. Each category gets its amount again, and whatever was not spent last month is gone from the plan even though the cash is still in checking, which is why leftover money tends to be spent twice. A rollover changes that for one category at a time: last month's difference, amount minus spending, carries into this month on top of this month's amount. Rollover belongs to the lumpy categories, where a month with nothing spent means the expense has not arrived yet, and not to the steady ones, where a leftover is a real surplus that should leave for savings.

In a sentence

• "Car maintenance rolls over, so three quiet months built a $300 balance before the $440 brake job."
• "With rollover on, April's $40 overspend starts May $40 down instead of vanishing when the month resets."
• "Groceries reset on the first; gifts roll over. One is a steady category and the other is a lumpy one."

How it works

Balance carried into this month = last month's carried balance + last month's amount − last month's spending

Available this month = balance carried in + this month's amount

1. Choose the categories that carry a balance. The lumpy ones: car maintenance, gifts, clothing, medical, annual renewals, and anything budgeted every three months or longer. Steady categories keep resetting.
2. Pick the month the balance starts from, and seed it with a starting balance if money was already set aside.
3. Each month, add the amount and subtract the spending. What is left carries; spending past the amount carries as a negative balance that the next month's amount fills first.
4. Pay the lumpy expense from the balance when it lands, and let the quiet months rebuild it.
5. Keep the balances covered by cash. The positive balances added together should fit inside checking after the bills due before payday, or the budget has promised the same dollars twice.

An example

A car maintenance category with a $100 monthly amount, rolling over from January with no starting balance.

Reset every month, the same category reads $340 over in April and $100 under in each of the three months before it, and the $300 those months did not spend has long since blended into checking. With rollover, April has $400 available against the $440 brake job, is $40 short rather than $340 over, and May's amount fills the hole. Over six months the amounts come to $600 and the repairs to $500, and the $100 balance at the end of June is the difference.

Why it matters

A monthly budget assumes each month pays for itself, and lumpy expenses break that assumption: the month they land in looks like a failure and the quiet months look better than they were. Rollover is the fix for exactly those categories, and it prevents two opposite mistakes. Rolling over nothing makes car repairs read as over in the one month a repair happens. Rolling over everything gives the steady categories a cushion with no purpose, and dining out drifts from $250 to $320 with the carried balance covering the difference and nobody deciding to spend more.

A carried balance is also a claim on cash that has to exist. When the balances exceed what checking holds after the bills, something was spent that the budget still counts as reserved, and checking one figure against the other once a month is what keeps a rollover honest.

Budget rollover versus a sinking fund

A rollover is a mechanism and a sinking fund is a purpose. A sinking fund is money set aside a little every month for an expense you know is coming; a category that rolls over is how a budget builds one, with the monthly amount as the share and the carried balance as the fund. The difference is where the cash sits: a sinking fund usually means the money moved to a savings account, while a rollover balance can stay in checking as long as the budget shows it as reserved rather than available. Rollover also carries the overspending that a fund never has to hold.

Common questions

Should I roll over unspent money or reset every month? Both, by category. Roll over the categories where a month with nothing spent means the expense is still coming, and reset the ones where it means you spent less; a budget that does one or the other for every category gets half of them wrong.

Does overspending roll over too? Yes, when the category rolls over. A category that goes $40 over starts the next month $40 down, and the monthly amount fills the hole before anything is available, which is more honest than resetting the category and pretending the overspend did not happen.

Is a rollover balance the same as savings? No. A carried balance in a lumpy category is a bill in slow motion, money reserved for an expense that has not arrived; savings is money that left the spending account for a named purpose. The two can share an account only if a list says which dollars are which.

How big should a carried balance get? Up to what the expense costs when it arrives, with a little margin. A balance that exceeds a full year of the expense means the monthly amount is too high; sweep the excess to savings and lower the amount.

Is a budget rollover the same as the envelope system? It is the same idea on paper. Cash left in an envelope at the end of the month stays in the envelope, which is the original rollover; a budget category does the same with a balance instead of bills, and can carry the negative balance an envelope cannot hold. See Envelope system.

Go deeper

• What to do with the money you didn't spend this month sorts every category into steady or lumpy and runs the end-of-month sweep.
• How to budget for bills that aren't monthly turns each non-monthly bill into a monthly share that accumulates in a carried balance.
• How to build a sinking fund, and how many to keep sizes the share, catches up a late start and keeps several funds in one account.

Where it shows up in Zypper

Zypper makes rollover a per-category switch. Turn on Roll over unspent budget for a category and what is left carries into the next month; the carried balance shows beside the amount, with a rollover chip whose hover shows the month's equation, the balance from last month plus this month's budget, minus what is spent and anything reserved for upcoming bills, equals what is remaining. Overspending carries as a negative balance. A Rolling over since month sets where the balance starts accumulating from, an optional Starting balance seeds it with money you had already set aside, and a cadence longer than a month turns rollover on automatically. See Rolling over unspent budget and Creating your budget for the details, or get started with Zypper to see your own carried balances.