When a modal verb is used in the perfect tense without a second verb, it is expressed in the perfect tense form. For example: Er hat das nicht gekonnt (He couldn't do it). Sie hat das nicht gewollt (She didn't want that). Ich habe nach Hause gemusst (I had [to go] home). However, when a modal verb is used in the perfect tense together with another verb, no perfect participle is used. Instead, the two verbs are given in their infinitive form. Example sentences:
The same rules apply for the past perfect with modal verbs and for the subjunctive past with modal verbs: