The three situations
| Situation | Provision | Commonest error |
|---|---|---|
| Change of scope | § 10 HOAI | no agreement in text form before performing |
| Due date and verifiability | § 15 HOAI | account without a traceable derivation |
| Several identical objects | § 11 HOAI | reduction overlooked or wrongly applied |
The first concerns the running contract, the second its conclusion, the third its structure. Together they cover the bulk of disputes. All three can be settled before the work begins.
Text form runs throughout
A pattern emerges once the relevant provisions are set side by side: the HOAI requires text form at a strikingly large number of points. It is thus the most frequently recurring formal requirement in the regulation.
It is required at eight points, which together cover the entire economic core of the contract. Where it is missing at one of them, the corresponding fallback rule applies.
| Where text form is required |
|---|
| Agreement on the level of the fee |
| Notice to consumers |
| Invoicing on partial commission |
| Valuation of incompletely transferred phases |
| Conversion supplement |
| Increase for repair works |
| Adjustment for changes of scope |
| Remuneration of additional coordination effort |
That is no accident. Since binding price law fell away, the agreement has taken the place of the ordinance. What is not agreed follows either from a fallback rule operating against the designer, or not at all.
In practice: text form is not a formality but the replacement for the price law that was removed. An email suffices; signatures are not required.
When the fee falls due
The claim becomes enforceable only once two conditions are met: the work has been accepted, and a verifiable final fee account has been handed to the client. Both must be present cumulatively.
The second is the more significant in practice. An account that cannot be verified does not reduce the claim; it prevents it falling due. The fee exists but cannot be enforced until the account is presented in verifiable form.
The article on a verifiable final fee account covers the requirements in detail. It also states the period within which the client must object to a lack of verifiability.
Why disputes arise after the fact
All three situations share one feature: they are not perceived as a problem while the project runs. Only the final account makes them visible, and by then the work has been done.
| Situation | Why it goes unnoticed |
|---|---|
| A change of scope looks self-evident | the client voices a wish, the designer implements it, and both assume it will sort itself out; it does not |
| The final account is prepared at project end | the parties are engaged on other schemes and no longer have the basis of the account in mind |
| Repetition reduction is not examined at contract stage | at that point it is often still open how many objects will actually follow |
A simple countermeasure covers all three: what must be agreed is agreed before the work is performed. After that the designer negotiates from a weaker position, because the work already exists.
The three deeper articles in this branch
The article on changes of scope covers the conditions under which the fee basis is adjusted and which changes fall outside them. That article also sets out which changes leave the calculation basis untouched.
The article on a verifiable final fee account covers the entries required and the consequences of unverifiability. An account without these particulars does not trigger enforceability.
The article on repetition reduction covers the conditions and the staging of the reduction across several objects. That article also explains why the reduction can apply to a later follow-on commission.
What has changed since 2021
The points of dispute have shifted without becoming fewer. They now concern content rather than price.
The shift can be set out side by side, and it explains why the service profiles have gained in importance. The dispute has not disappeared, it has changed subject.
| Until 2021 | Since 2021 | |
|---|---|---|
| Subject of dispute | the level of the fee | what is owed for the agreed amount |
| Typical questions | minimum rate met, fee zone, chargeable costs | scope of the work phase, basic against special services |
| Yardstick | the regulation | the agreement, failing that the service profile |
The service profiles have thereby gained significance. They are the only normed catalogue of what a work phase comprises, and they serve as the measure even where a lump sum fee has been agreed.
A reversal of priority follows for practice: precisely describing the scope now matters more than deriving the amount. Whoever negotiates only the amount negotiates the smaller half of the contract.
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.