Contractual obligation refers to a legal agreement between two parties that binds them to fulfill certain terms and conditions. In case you are writing a report or an article, using the same word repeatedly may not be ideal. Therefore, you can consider other synonyms that can be used interchangeably. Some common synonyms to contractual obligation include legal commitment, duty, responsibility, mandatory agreement, promise, and undertaking. Therefore, when writing about a contractual obligation between two parties, you can use these alternative synonyms to offer diversity and make your document more interesting. Additionally, using synonyms helps in avoiding redundancy and enhances the clarity of your message.