Planning permission for the 200sqm space was due to expire later this year, but the council has extended the terms of business, allowing it to continue operating until March 2017.
The steel and polycarbonate structure was built in 2006, being fabricated off-site and assembled using hydraulic lifts. It is known for its night-time polychromatic glow that lights up the South Bank.
It can hold up to 80 guests for a lunch or dinner, or 120 for a standing reception.
Kat Parker, head of sales and hospitality events at The Deck, said: "The Deck may only be a small structural addition to the National Theatre at 200sqm, but it has made a massive financial contribution to our business model. The Deck’s performance within the first five years of trading has dramatically outstripped initial predictions, and the National Theatre’s corporate entertaining commitment has gone from strength to strength.
"The extension of The Deck’s planning permission for another five years will give us the opportunity to further develop the venue side of the business and capitalise on event organisers’ interest in using and being associated with such an iconic brand as the National Theatre."
The Deck was shortlisted for the British Construction Industry Small Civil Engineering Award and was a finalist of the Prime Minister’s Better Public Building Award in 2009.
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