Der Kuchen muss gebacken worden sein.

Der Kuchen hat gebacken werden müssen.

Is it indeed true that there are two ways to use modal verbs in German? One where the modal changes tense, and one where the full verb does?

Is it just that the modal can stay in the present while the main verb goes into Perfekt? I notice this works in Active Voice as well:

Der Kuchen muss gebacken haben.

But it doesn't seem like any other tense works with that (with the modal staying in the present)

  • German modal verbs are not defective as their English counterparts - infinitive and perfect participle exist. This means that there are more ways they can be used. It just depends on what you wnat to express.
    – RHa
    Commented Feb 20 at 7:31

3 Answers 3


Correct, no other tense works like this because no other tense than the perfect uses a present-tense finite verb.

The ambiguity in construction arises because two different ways of constructing verb phrases interact here: a verb can be qualified by a modal verb, and it can also be subordinated to an auxiliary verb. And it turns out you can apply these constructions in either order.

As usual, when different surface forms exist, they tend to be used to convey at least slightly different meanings. In this case,

  • "Der Kuchen muss gebacken worden sein" = "The cake must be ready" (e.g. "before the party can begin"). Alternatively, this can convey a subjective meaning: "They must have (already) baked the cake (judging by the crumbs in the sink)".

  • "Der Kuchen hat gebacken werden müssen" = "It has proved necessary to bake a cake" (e.g. "because the child could not be made to cooperate with the exam otherwise").


Well, sometimes.

The two first examples are correct but no one would talk like in the second sentence.

In your example "gebacken" already expresses a completed action in which there is a necessity or assumption that the cake was baked at some point in the past.

In the perfect tense, one would typically express the completed past of a main verb, but since "müssen" is used here as a modal verb to signal an assumption or necessity in the past, and "gebacken haben" already represents the completed action, the sentence remains unchanged in its meaning and form.

The first sentence is already in a form that expresses a completed action so it can be Perfekt as well.


Is it indeed true that there are two ways to use modal verbs in German?

Yes. The difference is the viewpoint. Compare.

Ich habe einen Kuchen backen müssen.

This means that both events, the compulsion to bake and the baking, happened in the past.

Ich muss einen Kuchen gebacken haben.

This on the other hand means that the baking happened in the past but the compulsion has not. You my now ask yourself: “How does this even make sense?”

German tense understanding comes to your rescue. — That is, think of the only way that this makes sense. That's a common pattern in German. You try to make sense of it.

You cannot believe it. That's how it makes sense.

So this latter sentence means that you cannot believe that you baked a cake. But you did. In hindsight, it must have happened … somehow.

So with the modal modifying a perfect expression, you talk about hindsight, and the modal must be understood subjectively.

Also, that viewpoint is not limited to Perfekt tense but can be used in all the modal perfect tenses. As they all employ the Infinitiv II. That's the Partizip II + haben/sein. Compare:

Ich muss einen Kuchen gebacken haben. (Präsens+Infinitiv II)

Ich musste einen Kuchen gebacken haben. (Präteritum+Infinitiv II)

Ich werde einen Kuchen gebacken haben müssen. (Futur I+Infinitiv II)

(Es heißt,) ich müsse einen Kuchen gebacken haben. (Konjunktiv I+Infinitiv II)

Ich müsste einen Kuchen gebacken haben. (Konjunktiv II+Infinitiv II)

Ich würde einen Kuchen gebacken haben müssen. (Konjunktiv II Futur I+Infinitiv II)

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