Declension table of ?kartavyatva

Neuter	Singular	Dual	Plural
Nominative	kartavyatvam	kartavyatve	kartavyatvāni
Vocative	kartavyatva	kartavyatve	kartavyatvāni
Accusative	kartavyatvam	kartavyatve	kartavyatvāni
Instrumental	kartavyatvena	kartavyatvābhyām	kartavyatvaiḥ
Dative	kartavyatvāya	kartavyatvābhyām	kartavyatvebhyaḥ
Ablative	kartavyatvāt	kartavyatvābhyām	kartavyatvebhyaḥ
Genitive	kartavyatvasya	kartavyatvayoḥ	kartavyatvānām
Locative	kartavyatve	kartavyatvayoḥ	kartavyatveṣu

Compound kartavyatva -

Adverb -kartavyatvam -kartavyatvāt