Hello student to be true each and every chapter of your class 11 syllabus is important for your board examination. However some  are very important to build you Basic concepts and without knowledge of that chapters studying class 12 is very difficult are mentioned below -

1)journal

2)ledger

3)theory of accounting

4) Bank reconciliation statements

5)recording of transactions

6)financial statements

7)application of computer In accounting

Feel free to comment if you have any doubt

Good luck