The basic rule
Where not all work phases are transferred, only the percentages provided for the phases transferred may be calculated and agreed. The agreement must be in text form.
The arithmetic is straightforward: the table value corresponds to 100 per cent for all nine phases, and what is invoiced is the sum of the percentages of the phases commissioned. Difficulty arises only where a phase is transferred in part.
| Commission | Percentages for buildings |
|---|---|
| Phases 1 to 4 only | 27 per cent |
| Phases 1 to 5 only | 52 per cent |
| Phases 5 to 7 only | 39 per cent |
| Phase 8 only | 32 per cent |
| All phases | 100 per cent |
The percentages differ between buildings and interiors. The full overview sits in the article on the nine work phases.
Phases transferred incompletely
It becomes harder where not all basic services within a phase are transferred. A rule exists for that too: only a fee corresponding to the share of the basic services transferred within the whole phase may be invoiced. The same applies where substantial parts of basic services are not transferred.
Here lies the practical difficulty: the HOAI does not weight individual basic services. The smallest unit weighted by the ordinance is the work phase. Within a phase there are no official percentages for the individual items of the catalogue.
The share must therefore be agreed, and in text form. In practice, firms rely on published assessment tables from the professional literature allocating percentages to the basic services of each phase. Those tables are usable and widely applied, but they are not requirements of the ordinance.
A recommendation for the contract follows: where a phase is transferred incompletely, name the assessment table relied upon. Otherwise the parties later argue about which source should govern.
Additional effort on isolated commissions
A phase commissioned in isolation generates more effort than the same phase within a continuous commission. Familiarisation, establishing the basis and preparing the output all arise in full, whereas in a full commission they are spread across several phases.
The ordinance addresses this in two places, and both presuppose an agreement. Without one, the extra effort stays with the designer.
For concept design and developed design as standalone services it provides a separate calculation rule. That arrangement is common, for instance in feasibility assessments before a site decision or in developing a competition entry.
For additional coordination or familiarisation effort it provides for separate remuneration, to be agreed in text form. Absent that agreement there is no entitlement to it.
The second point is almost never used in practice, although it is the appropriate answer to a common situation: taking over a project from a mid-stage work phase, where a predecessor's work must first be assimilated. The effort is real, but it appears in no weighting.
The typical arrangements
| Arrangement | Share | What to watch |
|---|---|---|
| Commission up to consent | 27 % | the client then awards to a main contractor; the design substance has been fully delivered |
| Commission without detailed design | 75 % rather than 100 % | the contractor takes on the detailing; responsibility for construction quality shifts and should be expressly regulated |
| Commission for supervision only | 32 % | the heaviest single phase; the incoming designer assimilates someone else's design without that effort appearing in the weighting |
| Staged commissioning | initially the early phases | the option conditions need regulating, since an unexercised option removes the basis for pricing the whole commission |
The provision on familiarisation effort applies directly to the third arrangement. It is also the one in which it is least often agreed.
What to watch when invoicing
Three points govern whether an invoice can be verified on a partial commission. All three concern the derivation rather than the level.
| Point | Why |
|---|---|
| Name the phases commissioned | not merely the percentage total; the client must be able to follow how the percentage is composed |
| Where phases are incomplete, disclose the weighting | including the source relied upon, since the ordinance sets no values for it |
| Show services performed outside the commission separately | absent a commission there is no entitlement to payment; notice before performing is the most effective measure |
The requirements for a verifiable account are covered in the article on a verifiable final fee account. It also sets out which period verifiability triggers.
The economics of partial commissions
A point rarely voiced in negotiation: the percentages reflect the average effort of a phase within a full commission. On a partial commission that assumption no longer holds.
Three effects work against the designer. They arise independently of one another and accumulate.
| Effect | Why it bites harder on a partial commission |
|---|---|
| Set-up effort arises in full | project set-up, contract clarification, familiarisation and lines of coordination arise whether one phase or eight are commissioned |
| Output preparation arises in full | work handed to another party must be prepared for handover; within a continuous commission that step falls away |
| Interfaces multiply | every handover to another designer creates coordination effort that neither side invoices alone |
It follows that a partial commission at the bare percentage is routinely under-recovered. Since binding price law fell away this can be reflected contractually, and the ordinance expressly names coordination and familiarisation effort as an anchor.
The link to the cost calculation model
One particularity concerns contracts ending before work phase 3. Since the fee for all basic services is derived from the cost calculation, a commission running only to phase 2 lacks the actual fee basis.
For that case the ordinance provides that the results of the cost estimate are used exceptionally. That is the only situation in which the cost estimate determines the fee, and it belongs named in the contract.
The system is covered in the article on cost framework and cost estimate. It also sets out at which level of the cost structure the estimate must be prepared.
Related articles
This article reflects the position of the rules and case law at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.