Some operating costs shrink when a building empties out; others don't move at all. Gross-up exists to stop that mismatch from landing entirely on whichever tenants happen to still be paying rent.
Key takeaways
An operating cost statement that grosses up a line item looks, at first read, like the landlord charging more than it actually spent. It usually isn't. Gross-up exists to solve a real mismatch between how a building's costs behave and how a building's occupancy behaves, and understanding that mismatch is most of what's needed to explain the adjustment convincingly.
Some operating costs are fixed regardless of how full the building is — property taxes and the base insurance premium don't shrink because three units sit empty. Other costs scale with occupancy — janitorial service, utilities in common areas, waste removal, and similar line items rise and fall with how many tenants are actually using the building day to day. In a partly vacant building, the fixed costs stay the same but get divided among fewer paying tenants, and some of the variable costs don't fall proportionately either, because a building still needs to be cleaned, lit, and serviced even at reduced occupancy. Left unadjusted, the occupied tenants end up absorbing costs that exist, in part, because other units are empty — not because of anything the occupied tenants are doing.
“Landlords deal with this asymmetry through a gross-up clause, which adjusts variable expenses upward as if the building were 95–100% occupied.” In practice, that means the landlord recalculates what the variable-cost pool would have been had the building been at the target occupancy, and divides that larger, hypothetical total among the tenants who are actually there, using each tenant's normal proportionate share. It is not a mechanism to recover more money than the landlord spent — the landlord's total collection across all tenants generally still can't exceed 100% of actual cost under most leases — it changes how that actual cost gets allocated among the tenants who are present.
A common point of confusion is grossing up the entire operating cost bill rather than just its variable component. Fixed costs — property tax, the building's base insurance premium, a management fee calculated as a flat percentage of base rent rather than of collected operating costs — typically pass through at their actual dollar amount, full stop, regardless of occupancy. The same reconciliation letter that explains a CAM variance should draw this line explicitly for a tenant asking about a gross-up adjustment: which costs were grossed up, which weren't, and why the distinction exists.
There's no market-wide rule setting the gross-up target at exactly 95% versus 100%, or at some other figure entirely — it's a negotiated term specific to the lease in front of you, and it should be read rather than assumed to match the last building's number. A tenant exercising an audit right over a reconciliation that includes a gross-up adjustment is entitled to see the calculation itself, not just the resulting number, precisely because the target percentage and the underlying variable-cost split are both negotiated inputs rather than fixed facts a tenant could otherwise verify independently.
Typical fixed vs. variable split
Per Treadstone Law’s own breakdown of gross versus net Ontario commercial leases: Usually fixed (billed at actual, never grossed up): property taxes, base building insurance, a flat-rate management fee.
Usually variable (the pool a gross-up clause applies to): janitorial and cleaning, common-area utilities, waste removal, seasonal landscaping and snow clearing where billed per-service rather than as a fixed annual contract.
Worth confirming case by case: HVAC energy for common areas, which can be structured either way depending on the building's metering.
Operating cost reconciliation isn’t unique to gross-up — Treadstone Law’s own overview of Ontario commercial leases notes that the operating-cost charge generally “is not a fixed number — it is estimated at the start of the year and reconciled at the end,” and gross-up is one input into that year-end reconciliation, not a separate calculation running on its own. Because gross-up depends on two inputs a tenant can't independently observe — actual occupancy through the year and the split between fixed and variable costs — the calculation is a natural target for an operating cost audit. A tenant exercising that right is entitled to see how the landlord arrived at the grossed-up figure, not just the final number on the statement: the actual variable-cost total, the occupancy percentage used, and the target percentage the lease specifies. A landlord that can produce those three inputs on request rarely has a gross-up dispute turn into anything more than a clarifying conversation.
A 50,000 sq. ft. building is 70% occupied — 35,000 sq. ft. leased. Actual variable operating costs for the year come to $250,000.00. Grossed up to a 95% target occupancy, that figure becomes $339,285.71 — calculated as the actual cost divided by actual occupancy (70%), then multiplied by the target occupancy (95%): $250,000.00 ÷ 0.70 × 0.95.
A tenant occupying 2,200 sq. ft. — 4.40% of the building — would pay $11,000.00 on the ungrossed actual figure, or $14,928.57 on the grossed-up figure: a difference of $3,928.57 for this one tenant alone. That gap is the exact amount the gross-up clause is designed to shift away from the occupied tenants and back onto the landlord as the cost of carrying vacant space — without it, the tenant would be paying more per square foot specifically because other units in the building are sitting empty, which is precisely the outcome the clause exists to prevent.
It can, in a fully or near-fully occupied building, since grossing up variable costs to 95–100% when the building is already at 90% or more moves the number only slightly, but it still moves it upward rather than leaving it at the true actual figure. Tenants negotiating a lease sometimes push for gross-up to apply only below a stated occupancy threshold, so it doesn't add anything when the building is already close to full.
No — it's a negotiated clause, not a default rule or a statutory requirement. A lease with no gross-up provision simply passes through actual costs as incurred, which can mean occupied tenants do absorb more per square foot during a period of higher vacancy, unless another mechanism in the lease addresses it.
Not under a standard gross-up clause — fixed costs are, by definition, the costs that don't move with occupancy, so grossing them up wouldn't reflect anything real. If a lease's gross-up language is broad enough to sweep in fixed costs, that's worth flagging specifically, since it departs from how the clause is typically structured.
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