The Aegis-owned agency is understood to be discussing the details of a new contract after a review process that saw rival agencies drop out of the contest against Carat.
It appeared that OMD would pitch against Carat in the final round but the agency withdrew from the process.
It is understood that as part of the process, agencies were asked to participate in a closed online auction.
Keith Moor, Santander's director of brand and communications, handled the process. Santander last held a review in 2008 after Santander merged Abbey, Alliance & Leicester and Bradford & Bingley.
Last year, the company conducted a statutory review of its ad account, which had been held by Engine. After a pitch process that included Grey and Leo Burnett, the business stayed with the incumbent.
Santander said that the review is ongoing.