The offer, which runs until 31 December 2010, means selected models from the Ibiza, Leon, Altea, Altea XL and Exeo ranges will be sold with 17.5 per cent off the normal price.
In the case of the Seat Leon 1.4 TSI Sport, this would mean a saving of nearly 2,700 from £18,055 to just £15,365.
Seat has announced the discounts to sell more cars before VAT prices rise to 20 per cent from January 2011.
Seat UK Head of Marketing Steve Robertson said: "With the VAT increase coming early next year there really has never been a better time to take advantage of this terrific offer.
"Simple, straightforward and extremely attractive this generous incentive should put Seat at the very top of new car buyers’ lists."
The offer applies to all Ibiza SC and 5dr models but not the Cupra and Cupra Bocanegra. All Altea and Altea XL versions are included in the offer, as are all Exeo and Exeo ST variants with the exclusion of the SE Tech and Sort Tech specification models.
Finally, The , S Emocion, SE and Sport models will all be available with 17.5 per cent discount until December.
Seat has improved its market share to 1.61 per cent in the UK market this year, with an emphasis on fleet sales boosting new car registrations. In keeping with this strategy, Seat is also opening the offer to small local business sales.