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Rollover is one of CashCat’s most powerful features. Instead of losing unspent budget at month’s end, money automatically carries forward, letting you build up categories over time.

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How rollover works

At the end of each month, CashCat calculates how much you didn’t spend from each category: 
Rollover = (Previous rollover + Money assigned) - Money spent
This amount automatically becomes available in the next month, added to whatever new money you assign.

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Example

Let’s say you have a “Car Maintenance” category: January:
  • Assigned: $100
  • Spent: $0
  • Rollover to February: $100
February:
  • Starting rollover: $100
  • Assigned: $100
  • Spent: $50
  • Rollover to March: $150
March:
  • Starting rollover: $150
  • Assigned: $100
  • Spent: $400 (new tires!)
  • Rollover to April: -$150
The negative rollover in March means you overspent and need to catch up in April.
Rollover calculations happen automatically. You never need to manually move money between months.

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Categories with rollover enabled

Not every category needs rollover. The rollover_enabled flag lets you control this per-category. Good candidates for rollover:
  • Irregular expenses (car repairs, medical, gifts)
  • Sinking funds (annual insurance, property tax)
  • Savings goals (vacation, new computer)
  • Emergency funds
Categories that might not need rollover:
  • Fixed monthly bills (rent, subscription services)
  • Groceries and regular spending
  • Any category where you want a fresh start each month
Consider enabling rollover for categories where expenses are unpredictable or occur less than monthly.

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Viewing rollover amounts

When you query groups or categories for a specific month, the API calculates rollover from all previous months: 
GET /api/v1/groups?include_budget_totals=true&month=2024-03
The response includes:
  • month_assigned — New money assigned this month
  • month_spent — Total spending this month
  • month_rollover — Amount carried forward from previous months
  • month_budget_left — What’s left (assigned + rollover - spent)
Rollover calculations go back to the first month where you made any assignments. If you’ve been using CashCat for years, these calculations include your entire history.

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How rollover is calculated

For each category, CashCat:
  1. Finds the earliest month with an assignment
  2. Walks forward month-by-month
  3. For each month, calculates: rollover = previous_rollover + assigned - spent
  4. Stops at the target month
This means rollover for a category in December 2024 includes:
  • Everything assigned since you started using the category
  • Minus everything spent over that time
  • Minus any months where you didn’t assign enough to cover spending

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Performance considerations

Rollover calculations can be intensive for:
  • Many categories
  • Long time periods
  • Lots of transactions
CashCat calculates rollover on-demand when you request budget totals. The system is optimized to handle thousands of transactions, but be aware that complex queries may take a moment.
The API fetches assignments and payments in batches to handle large datasets efficiently.

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Negative rollover

If you spend more than you have assigned (including rollover), you get negative rollover. This shows categories where you’re behind budget. What negative rollover means:
  • You overspent in previous months
  • You need to assign extra to catch up
  • Or adjust your goal if the category consistently runs over
Negative rollover isn’t necessarily bad—it just means you’re tracking reality. Maybe your grocery budget was too low. Adjust it going forward.

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Zero-based budgeting and rollover

Rollover supports zero-based budgeting by letting you:
  1. Budget for irregular expenses — Assign a little each month, spend when needed
  2. Build savings gradually — Watch categories grow over time
  3. Handle overspending — See exactly where you’re behind and recover
  4. Stay flexible — Edit past transactions and rollover updates automatically
You still give every dollar a job when income arrives, but rollover means those dollars can wait in their assigned categories until you need them.

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Rollover and goal types

Different goal types work naturally with rollover: Spending categories
Rollover accumulates excess for future spending. If you budget 100forentertainmentbutonlyspend100 for entertainment but only spend 60, that $40 is available next month. Savings categories
Rollover is essential—these categories are meant to grow over time as you work toward a goal. Emergency funds
Rollover builds your safety net month by month until you reach your target, then maintains it.
You can disable rollover even for savings goals if you want to enforce a “save this much every month” approach instead of accumulating.

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Starting mid-month or mid-year

When you start using CashCat, rollover calculations begin from your first assignments:
  1. Create your categories
  2. Add your first month’s assignments
  3. Record transactions as they happen
  4. Next month, rollover appears automatically
You don’t need to enter historical data—just start fresh and let rollover build from there.

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Rollover vs transfers

Don’t confuse budget rollover with account transfers: Rollover is about budget categories (conceptual money). Unspent budget in the “Groceries” category carries forward. Transfers move actual money between accounts (physical money). Moving money from checking to savings. They’re independent:
  • Rollover happens automatically within categories
  • Transfers you create manually to move money between accounts
  • Transfers don’t affect category budgets
  • Rollover doesn’t move money between accounts

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