The clause that hides in plain sight
Most tenants read a commercial lease the way they read a terms-of-service screen: scanning for the rent number, skimming the rest, signing where the broker points. The operating expense section gets a polite nod. And buried in that section, often a single sentence long, sits a provision that can quietly move thousands of dollars a year in either direction.
It usually reads something like this: Landlord may adjust variable operating expenses to reflect the amount that would have been incurred had the building been 95% occupied. That sentence is the gross-up provision. It looks like accounting housekeeping. It is, in fact, one of the few clauses in your lease where the math can work entirely for you or entirely against you, depending on a single year you may not even be paying attention to.
Why occupancy changes the bill
To understand the gross-up, you first have to see that a building's operating expenses come in two flavors.
Some costs are fixed. The property taxes, the insurance premium, the landscaping contract—these stay roughly the same whether the building is packed or hollow. Snow still has to be cleared from an empty parking lot.
Other costs are variable. They rise and fall with how many tenants are actually in the building. Janitorial service scales with occupied square footage—nobody cleans a vacant floor nightly. Electricity and water for tenant spaces track with use. Management fees are often calculated as a percentage of collected rent. When a building sits half empty, these variable costs drop, simply because there are fewer people generating them.
That seems like good news for a tenant. If the building is only 60% full, the janitorial bill is lower, so my share of operating expenses should be lower too. And in a single isolated year, it is. The trouble is that commercial leases almost never bill operating expenses in isolation. They bill them in comparison to a fixed reference point—and that's where the gross-up earns its keep.
The base year, and the trap inside it
Many office leases are written on a base-year structure. In your first year, the landlord absorbs the building's operating expenses; that year's total becomes your base. From then on, you pay only your proportionate share of the increase over that base year. The base year is the floor, and everything you'll ever pay in escalations is measured upward from it.
Now imagine you sign during a downturn, and your base year happens to land while the building is 60% occupied. The variable costs that year are artificially low because two-fifths of the building is dark. Your base—your permanent floor—gets set unnaturally low.
Then the economy recovers. The building fills to 95%. Janitorial, utilities, and management fees all climb, partly from inflation but mostly because the building is simply busier now. Your operating expense increases look enormous, and you pay a share of every dollar above that depressed base. You're not paying for inflation. You're paying for the building lacing up its shoes after you locked in the price of it sitting still.
This is the base year gross-up trap, and it is the single most common way tenants overpay without anyone doing anything dishonest.
What grossing up actually does
A properly written gross-up provision fixes this by normalizing variable expenses to an assumed occupancy—commonly 95%, sometimes 100%—in every year, including the base year.
The calculation is straightforward in principle. The landlord takes the variable expenses actually incurred, divides by the actual occupancy rate, and multiplies by the assumed rate. If janitorial cost $60,000 at 60% occupancy, grossing up to 95% means estimating what it would have cost at 95%: roughly $60,000 ÷ 0.60 × 0.95, or about $95,000. Fixed expenses are left untouched, because they don't move with occupancy in the first place.
Applied consistently, this lifts the base year up to a fully-occupied equivalent. Your floor is now set as if the building were full. So when the building actually fills, the variable costs don't suddenly spike relative to your base—because your base already assumed a full building. The escalation you pay reflects real cost growth, not the building's recovery from vacancy.
The symmetry is the whole point. Gross-up protects the tenant in the base year by raising an artificially low floor, and it protects the landlord in later years by ensuring a building that fills up doesn't hand tenants windfall-low expenses. Done right, it makes the comparison honest in both directions.
Where the language quietly fails
The danger is that the provision is only as good as its wording, and the wording fails in predictable ways.
The most expensive failure is asymmetry: a lease that grosses up expenses in the comparison years but is silent about the base year. The landlord normalizes the years where high numbers help him and leaves the base low. That's the trap with a signature on it. Any gross-up clause you accept should explicitly state that the same methodology applies to the base year as to every subsequent year.
Watch the occupancy figure too. "95% occupied" and "100% occupied" are different floors, and a landlord using 100% in the comparison years while computing the base at a lower assumption is quietly tilting the field. The assumed percentage should be the same number, everywhere.
Then there's scope creep. Gross-up should apply only to genuinely variable, occupancy-driven costs. A clause that allows the landlord to gross up fixed expenses—taxes, insurance, the security contract—is inventing inflation out of thin air, because those costs wouldn't have risen with occupancy anyway. The provision should name the categories it touches, or at minimum limit itself to expenses that vary with occupancy.
Reading it before you sign
You don't need to be an accountant to audit this clause. You need to ask four questions of the language in front of you.
Does the gross-up apply to the base year as well as comparison years? Is the assumed occupancy percentage identical across all years? Is it limited to variable, occupancy-sensitive expenses? And does the lease give you the right to see the landlord's reconciliation and the occupancy figures behind it, so you can check the arithmetic later?
If the answers are yes, yes, yes, and yes, the gross-up is doing its honest job. If any answer is no—or the clause simply doesn't say—you've found the most negotiable, highest-leverage sentence in the document, and it costs nothing to ask for it to be made symmetrical before the ink dries.
Why this is worth the half hour
The gross-up provision rewards exactly one behavior: reading the lease as a system rather than a list of numbers. The base year, the occupancy assumption, and the variable-cost definition only reveal their meaning when you hold them together. Most overpayment doesn't come from being cheated. It comes from a clause that was technically disclosed, never read in context, and compounding quietly for the length of a ten-year term.
That's the work closeout was built to make routine. It reads your lease's operating expense and gross-up language alongside the year-end reconciliations, flags whether the base year was grossed up symmetrically, checks the occupancy math against what you're being billed, and surfaces the questions worth raising before a deadline closes them off. The clause stops being a sentence you skimmed and becomes a number you can defend. If you want to see what your own lease is actually saying, you can start at closeout.lumenlabs.works—and you'll understand the gross-up either way.