The Hornets overcame Bostik League Premier Division outfit Potters Bar Town on Saturday thanks to a late winner from Chris Smith.
His 88th-minute goal gave the home side a narrow 1-0 victory and was the third time this season they have overcome higher-division opposition.
They will now find out their reward at 1pm today (Monday) when the FA publishes the third qualifying round draw.
A total of 44 clubs, from step two of the National League System enter at this stage, so Horsham, as well as being drawn against the remaining teams in the competition, could face any of 22 from National League South.
A win at this stage of the competition is worth £5,000 to the victors, with Saturday's win adding a further £4,000 to the prize money they have already bagged from their cup ventures this season.
Third round qualifying matches are scheduled for Saturday, November 24 2018