The Pilgrims defeated Norwich City RDP 4-3 at The Jakemans Stadium with Jackson's strike sealing victory following a cross from regular goalkeeper Nick Ivanov, who had emerged as an outfield substitute during the second half.
United's other goals were scored by Jenson Bark, Lewis Bontoft and Jack Bastow.
Boston (4-1-4-1): Jake Frestle; Nathan Stevens, Craig Forbes (Will Jackson 46), Daniel Fisher, Owen Sears; Marshall Young; Xander Crashley (Nick Ivanov 75), Lewis Bontoft, Jenson Bark, Jamie Gaukroger; Jack Bastow (Dougie Barrett 90). Sub (not used): Harrison Holland.