Seaton was last seen during the morning on Monday August 24 by work colleagues in Salisbury and has not been heard from since.
Wiltshire police have appealed for anyone with information to come forward.
Detective Inspector Simon Watson said: “It is very out of character for David not to make any contact with his family and we are increasingly concerned for his safety.
“Following enquiries David’s car has been found in Boscastle and we are working with colleagues in Devon and Cornwall Police to find him as quickly as possible.
“Teams of officers including the coast guard and police dogs are continuing their searches today in Boscastle and the surrounding area.
“I would like to appeal for anyone who has seen David or who has any information on his whereabouts to contact police.”
Joint managing director Ian Hammond says: “We can confirm David Seaton, our much loved colleague, has been reported missing.
“We do not believe that David’s disappearance is in any way related to his role as a director of Rowanmoor Pensions.
“The police are now searching for David and our thoughts are with his family at this difficult time.”
Hammond and Seaton led the Rowanmoor Pensions management buy-out of James Hay Consultancy in 2006.