Two contractors bid for the same forty-desk office in Holborn. One quotes a flat £2,900 a month, everything included. The other sends a rate card — so much per operative hour, windows priced by the drop, periodics on their own lines. The first number is easier to carry into a board meeting. That does not make it the better deal.

The choice between a fixed price and a schedule of rates is the most consequential decision in an office cleaning agreement, and it usually gets made for the wrong reason: whichever quote is simpler to explain upstairs.

What do fixed-price and schedule-of-rates contracts actually mean?

Fixed-price — sometimes called comprehensive or lump-sum — is a single agreed fee for a defined specification, paid every month regardless of how many hours the work actually takes. The contractor carries the risk. If the spec turns out to need more labour than they priced, that is their problem, not yours. In theory.

Schedule of rates runs the other way about. You agree unit prices up front — a rate per operative hour, another for each periodic task such as a carpet extraction or a window clean — and you pay for what gets measured and delivered. The rates are fixed. The total is not. It rises and falls with what the building genuinely needs that month.

The distinction most buyers miss is about incentives. Fixed-price hands the contractor a motive you might not want in the building. Their margin is the gap between your flat fee and their costs, and the one variable they control completely, without ever asking you, is how many hours they put on site.

Where output specifications fit in

Fixed-price contracts usually arrive dressed as output specifications — “the office will be maintained to an agreed standard” rather than “two cleaners, three hours a night.” That framing sounds appealing because it moves the argument from hours to results. An output spec with no real monitoring behind it, though, is just a fixed price with the hours painted out, and painted-out hours are hours that quietly shrink.

Which model gives you the predictable budget?

Fixed-price, plainly. Predictability is its whole appeal and the appeal is real.

A finance director wants one line in the budget that does not move. Fixed-price delivers exactly that: a set figure, twelve times a year, no awkward spike the month someone orders an extra window clean. For an office with stable occupancy and a scope that honestly never changes, that steadiness is worth a small premium.

The catch sits underneath the comfort. A price that never moves still has to absorb every fluctuation in cost somewhere, and the contractor absorbs it through the only lever they hold quietly: labour on site. The month they are stretched thin across other accounts, your Friday cover drops from two hours to one. Nobody rings to tell you. The invoice reads identically.

The problem with a price that never moves

This is the quiet failure mode of fixed-price cleaning, and it is everywhere. Service degrades in increments too small to justify a complaint. The bins get emptied, the obvious desktops get wiped, and the high dusting and the behind-the-monitors detail slip by a week, then a fortnight, then off the rota altogether. By the time someone finally notices, the thinner service has been normal for months, and clawing the hours back means opening a fresh negotiation from a weak position. An output spec only holds the line if you run a proper regime behind it — logged inspections and a monthly review someone genuinely attends. Most small and mid-sized offices never set one up, which leaves the standard resting entirely on the contractor’s conscience.

Which model copes with how London actually works now?

The two models genuinely diverge here, and it is where fixed-price shows its age.

Most London offices no longer fill up five days a week. Occupancy peaks Tuesday to Thursday and thins hard at both ends of the week; a great many floors sit half-empty by Friday lunchtime and dead by the evening. A fixed-price contract priced around a five-day office keeps marching the same crew through an empty building on the one day it needs them least. You are buying Friday cleaning at Wednesday prices.

Schedule of rates bends to that shape. If the floor runs at forty per cent late in the week, you specify a lighter touch for those days and pay a rate to match. When the headcount grows and the midweek gets heavier, the rate structure takes the strain without anyone reopening the entire contract. The pricing follows the building rather than a guess made at tender.

Underneath both models sits a cost floor that shapes everything. London cleaning is labour, and labour in London has a number attached. The London Living Wage rose to <cite index=”3-1″>£14.80 per hour, announced on 22 October 2025</cite>, while the statutory National Living Wage <cite index=”6-1″>will increase to £12.71 per hour from 1 April 2026</cite>. That gap — better than two pounds an hour, on every hour worked — is where much of the difference between a cheap flat fee and a fair one actually lives. A suspiciously low fixed price is nearly always a price that quietly assumes the statutory floor rather than the London one, and assumes fewer hours than the specification implies.

There was a media company on Gray’s Inn Road — ninety-odd people, one long floor, the kind of place that runs on Thursday-night drinks and summer Fridays — that signed a five-day fixed-price contract because its incoming facilities manager wanted a single clean figure for her first board pack. Fair enough. The floor was reliably empty by two on a Friday and stayed that way. It took eighteen months and one distinctly grubby August before anyone realised they were paying full five-day cover for a building that operated four days and a bit. They switched to a rate-based model with a stripped-back Friday. The saving was real, and smaller than they had hoped, because the contractor promptly edged the weekday rates up to protect the account — which is the sort of thing that happens, and which nobody warns you about at signing.

Pricing the days nobody’s in

A properly built office cleaning spec in 2026 prices each day for what that day actually is. A heavier reset at the start of the week, then a light security-and-kitchen pass on the Friday when barely anyone is in. Fixed-price can be made to do this too, but only if somebody sits down and rebuilds the specification around real attendance data — and most fixed-price contracts are simply rolled over year on year with the old five-day assumption still baked into them.

How do one-off and periodic works get handled?

Schedule of rates quietly wins the periodics.

Carpet extraction, window cleaning, a builders’ clean after a fit-out, a deep kitchen scrub before an audit — these all sit outside the nightly routine, and with an agreed rate card each one gets ordered at a known price with no haggling. You want the carpets done before a client visit on Thursday; the rate already exists; it happens. The same holds for the unglamorous reactive stuff — sickness cover when a regular operative calls in, or the extra pass a building needs after a summer party overran. A rate card has a line for each of those. A flat fee has a phone call and a quote.

Under a fixed price, anything the contract labels “out of scope” triggers a variation quote, and a variation quote is a small negotiation you never wanted, usually priced with no competitive pressure on it at all because you are already tied in. The comprehensive contract sold to you as the thing that would save admin ends up generating its own.

The variation-quote trap

Watch the scope boundary closely. Fixed-price contractors tend to price the core tightly and treat the periodics as the earner. The deep cleans and the one-offs are where the margin the flat fee squeezed out gets quietly made back, at rates you never put out to competitive tender. Read what is included against what is billable before you sign, because that boundary line is precisely where a comfortable monthly figure turns expensive.

So which should your office actually choose?

If you run a small, stable office with predictable use and no appetite for policing anyone — fifteen desks, the same five days, nothing much ever changing — take the fixed price. The admin you save is worth more than the value you lose, and the value you lose is genuinely small.

For everyone else, which is most London offices now, I would lean toward a schedule of rates, or better a hybrid: a fixed core for the predictable nightly work, an open rate card for the periodics, and an occupancy-flexed spec that prices Friday as Friday. Fixed-price feels safer because it converts a messy operational question into one tidy number, and finance teams love a tidy number. The tidiness, though, is the product you are actually buying — not the cleaning — and the two are not the same purchase.

A workable middle

Most well-run London offices land somewhere between the pure models in the end. Fixed monthly for the base specification so the budget holds steady, with agreed rates for everything periodic so nothing has to be re-quoted under pressure. Then a written occupancy assumption in the contract itself, so the empty-day question gets answered on the page rather than absorbed in silence. Ask the contractor to show their hours. A fair fixed price and a fair schedule of rates should, for the same building, land in roughly the same place — and when a flat fee comes in well below the rate-based equivalent, the hours have already gone missing somewhere before you have signed a thing.

By Friday the floor is half-lit and mostly empty, and the size of the crew moving through it was settled months earlier, by which of the two numbers you put your name to.