The current store on Roman Road will close on Friday (April 16).
Bosses hope the new, bigger premises, which will also cover the former Six Acres Day Centre site, will open its doors in November this year, to coincide with the Christmas shopping rush.
Building workers moved onto the site weeks after Somerset West and Taunton Council granted planning permission for the scheme.
A Lidl spokesperson said the new store will see its sales area increase by 80 per cent to 1,410 square metres.
They added that it will offer “an even greater range of Lidl’s fresh, high quality and affordable produce”.
It will feature improved facilities to the in-store bakery and customer toilets, as well as 124 car parking spaces, including six disabled, nine parent and child and two electric vehicle charging spaces, alongside ample parking for bicycles.
Lidl is working with construction firm Adston to build the supermarket, which will retain all its existing employees, who will be working at nearby Lidl stores until work is complete.
Lidl GB’s regional head of property, Matthias Daly, said: “We are committed to delivering an attractive new offering to Taunton, which will allow for a larger, more modern store and enhanced shopping experience, whilst providing customers the full range of quality Lidl products at unbeatable prices.
“We are extremely grateful for all the support that we have received so far and would like to thank everyone for their patience and understanding whilst we enter this next phase of the development.”
The new supermarket is part of the company’s £1.3 billion investment in its expansion across Great Britain in 2021 and 2022.
Lidl’s other Taunton store in Castle Street is remaining open during the building work in Roman Road.