Declaration of the election result for this seat is anticipated to be around 4am but could be later with a high turnout reported from polling stations in both towns, according to Deputy Returning Officer Ian Fytche.
Mr Fytche said: “It will be a long night, but that’s democracy. It has to be right to encourage as many people as possible to get involved.
“Overall turnout is reported to be quite busy at polling stations in Sleaford and Hykeham today.
“Around 90 per cent of postal votes have been returned as well, compared to around 70 per cent last time in the by-election in December.”
They have received 90,925 postal votes, compared to around 88,000 last time.
The count for the general election will run alongside counts for by-elections for two North Kesteven District Council wards - Ashby de la Launde and Cranwell; and Heighington and Washingborough, plus there are by-elections for vacant seats on Quarrington Ward of Sleaford Town Council and Bracebridge Heath Parish Council and a Neighbourhood Plan referendum for NOcton and Potterhanworth.
To speed things up, counting for the parish and town councils and the referendum will be done in a separate room by extra staff after papers are verified.