^Divisions are sorted according to their level within the English football league system at the time which are shown in parentheses.
^On 9 April the Isthmian League EGM decided that, despite continual bad weather, the season would finish on 5 May as planned. Aldershot Town tried to arrange for the unplayed match to be played on the evening of 5 May, but Billericay Town refused to accommodate this arrangement. The Isthmian League Management Committee subsequently convened and ruled that no points would be allocated to either team.
^Gateshead were demoted to the National League North on 8 June 2019 because of financial irregularities. As a result Aldershot Town were given a reprieve from relegation.
^Season was curtailed in April 2020 on account of the COVID-19 pandemic with league positions being determined on a points-per-game basis.