The Department's functions and responsibilities include:
- Purchasing of books: books are ordered, receipted and processed by the Department
- Legal Deposit from British sources: on average, 85% of the Library’s new acquisitions (books and print serials) are acquired under legal deposit privilege. Every week the Library receives up to 1,500 books through legal deposit. The Department processes all these books
- Legal Deposit from Irish sources: the Accessions Librarian is responsible for identifying and claiming new titles from Irish publishers. About 2,400 new Irish titles are received each year. All books received are processed and acknowledged
- Irish Copyright Agency: the Department provides a clearinghouse service to the Bodleian Library, University of Oxford, Cambridge University Library, the National Library of Scotland, and the National Library of Wales legal deposit libraries. Irish publishers send copies of their publications to Trinity College Dublin for onward delivery to the Agency for the Legal Deposit Libraries in the United Kingdom
- Trinity College Dublin Theses: the Department receives and acknowledges Trinity College Dublin theses deposited by the Graduate Studies Office.
- Donations: the Department processes and acknowledges all donations to the Library
- Exchanges: the Department manages an exchange programme for publications with a number of universities worldwide