Declension table of kartavya

Neuter	Singular	Dual	Plural
Nominative	kartavyam	kartavye	kartavyāni
Vocative	kartavya	kartavye	kartavyāni
Accusative	kartavyam	kartavye	kartavyāni
Instrumental	kartavyena	kartavyābhyām	kartavyaiḥ
Dative	kartavyāya	kartavyābhyām	kartavyebhyaḥ
Ablative	kartavyāt	kartavyābhyām	kartavyebhyaḥ
Genitive	kartavyasya	kartavyayoḥ	kartavyānām
Locative	kartavye	kartavyayoḥ	kartavyeṣu

Compound kartavya -

Adverb -kartavyam -kartavyāt