How do I build a small business budget?

Start from last year's actuals, not a blank spreadsheet

The fastest way to build a credible budget is to export twelve months of actual revenue and expenses from QuickBooks Online or Xero and use that as the starting template, adjusting each line for what you already know will change. A budget built from a blank spreadsheet tends to miss expenses that only show up once or twice a year, like insurance renewals or annual software licences, because nothing prompts the person building it to remember them.

A business whose costs have not changed meaningfully in years can usually get away with adjusting last year's actuals line by line. A business going through significant change, a new location, a pivot in service lines, is often better served by a zero-based budget, which starts every line at zero and requires justifying each cost fresh rather than assuming it should simply continue at last year's level.

Build revenue from drivers, then split costs into fixed and variable

A drivers-based revenue budget breaks a single revenue line into the factors that actually produce it, such as number of clients multiplied by average job value, or units sold multiplied by price, rather than picking one total number and hoping it holds. Building revenue this way makes it possible to test what happens if the driver changes, for example, if average job value rises but client count stays flat, which a single top-line guess cannot show. A hypothetical example makes this concrete: a service business budgeting 40 clients a month at an average job value of $250 arrives at $10,000 in monthly revenue; if the driver assumptions change to 35 clients at $280 average job value instead, the total barely moves, but the business now knows exactly which lever, client count or average job value, actually needs attention if the target is missed. Building a best-case and worst-case version alongside the primary budget, adjusting only the revenue driver assumptions, shows how much cushion the business actually has if a slow month runs longer than expected. This does not need to be a separate full budget, just the same driver-based revenue model recalculated with a lower client count or average job value.

Fixed costs, like rent and insurance, stay roughly the same regardless of revenue; variable costs, like materials or subcontractor labour, move with sales volume and should be budgeted as a percentage of revenue rather than a flat dollar amount. A business with meaningful seasonality, a retailer with a strong fourth quarter, a landscaper with almost no revenue in January, needs monthly budget figures that reflect that pattern rather than dividing an annual total by twelve, since a flat monthly budget shows a false shortfall in slow months and a false surplus in busy ones. This same fixed-versus-variable split is exactly what feeds a break-even calculation, so building the budget and the break-even model from the same categories keeps the two consistent with each other.

Build in the big, irregular items before they surprise you

A budget that only covers routine monthly expenses misses the items most likely to actually cause a cash problem: a planned new hire and the timing of their first payroll, a capital purchase like equipment or a vehicle, HST remittances and income tax instalments, and owner compensation. Deciding owner pay as part of the budget, rather than treating it as whatever is left over at the end of the month, is one of the more common gaps in a first-time budget. In a business with more than one manager or department head, pulling each of them into the budget for their own area, rather than building the entire budget from the top down, usually produces more accurate numbers and more buy-in when it comes time to explain a variance later. A hiring plan belongs in the budget even before a candidate is identified, since the ramp time between deciding to hire and that person becoming fully productive is itself a cost worth planning for, not just their first paycheque.

Review it every month, and let it become a rolling forecast

A budget only earns its keep once it is compared to what actually happened, ideally on the same day every month, looking specifically at which lines moved the most and why. Our answer on monthly KPIs to track covers the handful of numbers worth watching alongside the budget-versus-actual review.

A budget set once a year and never revisited tends to drift out of relevance by the second half of the year. Updating it into a rolling forecast, extending it forward each quarter based on the latest actuals, keeps the numbers useful even as circumstances change. QuickBooks Online and Xero both include a built-in budgeting feature that compares actuals automatically, which is enough for many owner-operated businesses; a spreadsheet still works well for the driver-based revenue build itself.

How we build budgets with clients

As part of our CFO advisory work, we build the first budget directly from a client's actual accounting data, then walk through it together line by line so the owner understands where each number came from, not just what it is. Our bookkeeping team keeps the categories in the chart of accounts consistent with what feeds the budget, so pulling next year's actuals is not its own separate project. A budget an owner did not help build rarely gets used past the first month.