The project has a focus on non-traditional advertising elements, and is understood to be strategically focused, bypassing television, radio and press.
A spokesman for Deloitte confirmed that it had approached several creative agencies about a "number of non-advertising projects", but declined to comment further on the nature of the task.
He added that the review was separate to its current advertising account, which is handled by RMG. The WPP-owned integrated agency is unaffected by the search, but it is unclear if it will be involved in the pitch for the new project.
RMG's most recent national advertising campaign for Deloitte launched in March and was the company's largest investment in advertising for some time.
It promoted Deloitte's services, with messages including a "complete approach to business" and an "ability to view a problem from all angles".
The campaign included a 360-degree wrap that spanned 120x15 metres around the entirety of London's Imax Cinema, which is currently the largest outdoor site in the UK. It was implemented by Ocean Outdoor.
The campaign also included similar giant posters positioned outside of London and posters in key commuter train stations across the UK, as well as national print and online media.
Deloitte is a market-leader in financial and auditing services. It is part of the big-four global leaders, alongside Ernst & Young, PricewaterhouseCoopers and KPMG.