The Him & Her star will appear opposite Miranda's Sarah Hadland in the sitcom, which is set in a busy West Midlands Jobcentre.
"Incredibly excitedly excited to begin the new ITV adventure that is The Job Lot," said Tovey. "Superb scripts... gifted actors... and a Jobcentre... the dream."
Hadland added: "I challenge Russell Tovey to an 'excitement-off' over new comedy The Job Lot - I am more excited than him - great scripts, cast and of course [my character] Trish - a desperate woman with a very aggressive perm and a love of beige."
Tovey will play reluctant Jobcentre worker Karl, who works for Hadland's Trish alongside the sour Angela (Jo Enright) and new mother Danielle (Tamla Kari).
The Job Lot also stars Sophie McShera (Downton Abbey), Tony Maudsley (Benidorm), Martin Marquez (Hotel Babylon), Angela Curran (This is Jinsy) and Adeel Akhtar (Four Lions).
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Big Talk's Kenton Allen, executive producer, said: "The moment we read the script I immediately thought The Job Lot was a wonderfully warm comedy that brilliantly captured the spirit of these times.
"As a boy from Birmingham, it seems a very long time since we've had an original comedy from the beating heart of the UK. The Midlands renaissance starts here and I can't wait for the ITV audience to get to know all these brilliant characters."
"We're proud to be the home of this joyful, modern and warm sitcom," said ITV's Myfanwy Moore. "I'm so pleased we're able to support new writers, whilst working with such a truly impressive cast."