Town will now look to negotiate the best possible compensation deal they can for the 20-year-old midfielder, a target for clubs both in the Championship and Premier League according to chairman David Cardoza.
Cardoza, who admitted that Jacobs' decision was not a surprise, told BBC Northampton: "Any club has still got to reach our valuation and no-one has got there yet.
"We'll get the right price for him. We're going to work hard to make sure that we get adequately compensated."
Derby County have been the side linked most strongly with Jacobs to date, manager Nigel Clough confirmed his admiration of the player.