At present, there are two valid versions of the 50- and 1 000-krona banknotes. After 31 December 2013, you will no longer be able to pay with the older versions of the 50- and 1 000-krona banknotes that do not have foil strips.
If you still have such banknotes in your possession after 31 December 2013, the banks will be able to redeem them up to and including 28 February 2014.
50-kronor banknote without foil strips
1000-kronor banknote without foil strips