Invoice date vs date of payment

Hello,

I purchased a Laptop from Dell recently. The purchase order was raised on 26th of March againt a 'Performa Invoice'. The payment got cleared on 28th of March. Now the Tax Invoice send by Dell is of 5th of April 2013.

I was planning to adjust it in 2012/2013 books. Now I am not sure. Will the Laptop go into account books of 2012/2013 or 2013/2014?

Thanks,

Aseem