Arrear Salary Payment for last 8 (eight) years causing me to fall under 20% Tax Bracket in lieu of earlier 10% Tax Bracket

Hello Sir, I am a Central Government Employee and have been filing ITR since 1999. From 1999 to 2013, I filed it manually (ie. on paper). For the last two financial year, I am submitting it online. Recently I got an arrear salary payment from my office for a period of last 8 (eight) years – ie. from 2007 to 2015. This has happened since I got a promotion in 2007 and as per the provisions laid down by 6th CPC Report, my pay scale had to be revised. This revision has now taken place. For this I got a lumpsum arrear payment towards revised salary for the last eight years. Now the problem is that although I fall under 10% Tax Bracket, but due to this lumpsum arrear payment, my income for this current financial year is falling under 20% Bracket. As a result, my office is calculating the tax for this current year under 20% bracket and is deducting the same. Sir, had this salary been revised in 2007, this arrear payment would have been received by me as a part of my salary during the last eight years. Therefore, I could have got the opportunity to find my Income under 10% Bracket. Now, I would like to know, whether it is possible that I can submit revised IT Returns for these last 8 (eight) financial year because I think that would facilitate me to show my income still falling under 10% Bracket and I can have the rest 10% (20% - 10%) Tax refund from the IT Department, which my office is now deducting. If yes, kindly tell me about the procedure. Once again I would like to say, all my returns were submitted manually (on paper) except for the last two years and I have all the copies with me for records. Thanking you in advance – Rajib.