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How to Split One Utility Invoice Across Several Properties

One contract, one supply point, one PDF — and four flats, six apartments or three rented units behind it. Every property manager, landlord and accountant hits this eventually: the water contract is in the community's name, the whole building's electricity sits under a single supply point, the central boiler burns gas billed to one meter, and someone has to decide who pays what.

The tempting shortcut is to divide by the number of units, or by square metres, and move on. It works right up until a tenant disputes the figure, an auditor asks how you arrived at it, or a back-dated regularisation for a period nobody remembers lands in the middle of the quarter.

That's when you learn the real rule: a split you can't reconstruct is a split you can't defend. Here's a method that survives all three scenarios.

Three questions before you touch a calculator

Answer these first, because they determine everything downstream.

Whose name is on the invoice? If the supplier issues the bill in the occupant's name and you merely pay it on their behalf, you are advancing money. If the bill is in your name and you pass the cost on, you are selling them something — and that has tax consequences most people get wrong.

Is the consumption measured or estimated? A reading from a meter is evidence. A percentage is an opinion. The distance between them is where disputes live.

Which part of the bill is fixed and which is variable? Almost nobody asks this, and it's the single biggest source of unfair splits.

Step 1: choose the allocation key before the bill arrives

Deciding the key while looking at the amount is how bias creeps in. Fix the rule in the lease, the community bylaws or the internal procedure, then apply it blind.

There's a clear hierarchy, and you should always take the highest rung available:

Individual meter — actual consumption per unit. Unarguable.
Sub-meter or heat cost allocator — measured, if not perfectly, then proportionally.
An objective proxy — occupied nights, operating hours, staff headcount, treated m². Weaker, but observable.
An ownership coefficient — the participation quota, millesimi or permilage. Last resort, and only for costs that genuinely can't be individualised.

This isn't just good practice; it's roughly what European law now demands. The recast Energy Efficiency Directive (EU) 2023/1791 requires Member States to have transparent, publicly available national rules for allocating heating, cooling and domestic hot water costs in multi-apartment buildings supplied by collective systems. It requires individual meters where technically feasible and cost-effective, heat cost allocators on radiators where meters aren't, and — the deadline worth diarising — meters and allocators that aren't remotely readable must be made remotely readable or replaced by 1 January 2027, unless a Member State shows it isn't cost-efficient.

The national rules then fill in the detail:

Spain. Article 20 of the Ley de Arrendamientos Urbanos draws the line explicitly: services individualised by meter are the tenant's, full stop; general costs that can't be individualised follow the participation quota (or floor area where there's no horizontal-property regime), and only if the pact is in writing and states the annual amount at the date of contract. Royal Decree 736/2020 pushes central thermal installations toward individual metering and requires consumption and billing information to reach the end user at least every two months.
Italy. Article 1123 of the Civil Code splits expenses in proportion to the value of each property, unless agreed otherwise. But once heat accounting is installed, dividing heating purely by millesimi has been held illegitimate — consumption must follow what the devices actually recorded. UNI 10200 gives the working distinction: voluntary consumption (what the occupant chose, via the thermostatic valves) splits by the metering devices; involuntary consumption (distribution losses nobody controls) splits by heating millesimi.
Portugal. Article 1424 of the Civil Code sets proportionality to the permilage of each fraction as the default, but allows common-interest services to be charged in equal parts or in proportion to actual use — provided the condominium regulations say so, the criteria are specified and justified, and the resolution passes without opposition by a majority representing the majority of the building's value.

The pattern across all three is identical: measure if you can, use a coefficient only when you can't, and write the criterion down.

Step 2: split components, not totals

This is the step that separates a fair allocation from a lazy one.

A utility bill is not one number. An electricity invoice typically carries a fixed capacity term, a variable energy term, energy taxes, meter rental, sometimes reactive-power penalties, and sometimes a regularisation for an earlier period. Water bills carry a fixed service charge, consumption blocks, sewerage and waste fees. Gas is the same shape.

Apply the key per component:

Fixed charges exist whether anyone consumes or not. They follow the coefficient, not the meters. Charging the empty flat nothing for capacity it reserves all year is not fairness, it's a subsidy from the neighbours.
Variable charges follow measured consumption. This is the only part meters should drive.
Taxes and surcharges follow whatever base they're levied on — split them the same way you split that base, not by a separate rule.
Regularisations and credits follow the period they correct, not the period they arrive in.

That last one is the trap. A supplier's back-billing for last winter, allocated using this summer's tenant mix, charges the wrong people. If the occupancy changed, you need the *historic* key, which means your records have to be dated — another reason the criterion belongs in writing from day one.

Step 3: reconcile to the cent

The allocations must sum to the invoice total exactly. Not approximately.

Percentages produce fractions of a cent, and naive rounding leaves you a few cents short or long — trivial in isolation, corrosive at scale, and instantly noticed by the one owner who checks. Pick a documented rule (the largest-remainder method, where leftover cents go to the largest shares, is standard and easy to explain) and apply it consistently. Then assert the check: sum of parts equals total, every time, or the split doesn't ship.

Step 4: get the tax treatment right

In Spain this is where re-billing quietly goes wrong. Spanish tax doctrine has been consistent: when a landlord pays a supply invoiced in their own name and passes it to the tenant, that is not a disbursement made on the client's behalf, so it isn't excluded from the VAT base — it's a supply subject to VAT. It only qualifies as a true pass-through disbursement if the utility invoice is issued in the tenant's name. Same money, same meter, entirely different treatment, decided by whose name the supplier printed.

At EU level the Court of Justice addressed the related question in Case C-42/14 (*Wojskowa Agencja Mieszkaniowa*, 16 April 2015): where water, electricity, heating and refuse collection accompany a letting, they must in principle be treated as several distinct and independent supplies, assessed separately for VAT — unless the elements are so closely linked that splitting them would be artificial. The court pointed at metering as the deciding signal: where the tenant can choose their consumption and it's billed on individual meters, that's a separate supply from the lease.

Which closes a neat loop. Sub-metering isn't just an energy-efficiency requirement or a fairness mechanism — it's often what determines the tax characterisation of the recharge.

Step 5: keep the audit trail

For every split, keep six things together: the source PDF, the extracted line items, the meter readings with their dates, the key and its version, the calculation, and the resulting per-property amounts.

If a tenant challenges a figure eighteen months later, this file is the entire answer. If it lives in one person's spreadsheet and that person has left, you have no answer at all.

Where this actually breaks: getting the numbers off the PDF

Here's the honest part. None of the above is intellectually hard. The method fits on a napkin.

What kills it is that the inputs arrive as PDFs, photos and portal downloads, in a different layout from every supplier, and someone has to type the fixed term, the variable term, the taxes, the period and the readings into a spreadsheet before any of the logic can run. At twelve buildings and four supplies each, that's roughly two hundred re-keyed numbers a month — and every one is a chance to transpose a digit that then propagates, invisibly, into somebody's bill.

The classic fix was per-supplier OCR templates. They break the moment a supplier redesigns its bill, which is why per-supplier OCR templates are a maintenance treadmill rather than a solution. Modern AI extraction reads the document by meaning rather than by coordinates, which is what makes turning a stack of PDFs into a clean Excel sheet practical at portfolio scale.

Get the extraction right and the rest is arithmetic your spreadsheet already knows how to do. It's the same discipline that makes invoice capture worth automating and that pays off again during utility transfers after a sale, when the same bills have to be read all over again for a different purpose.

The short version

Decide the key before the bill arrives. Measure where you can, use coefficients only where you can't. Split fixed and variable separately. Allocate regularisations to the period they belong to. Reconcile to the cent with a documented rounding rule. Check whose name is on the invoice before deciding the VAT. Keep the file.

If the bottleneck is the typing rather than the thinking, WhappScan turns the bills you forward over WhatsApp into structured line items you can split.