I saw a few stickers on cash registers last week with pictures of Swedish notes crossed out and a date of June 30th.
A closer look showed the 20, 50, and 1000 kronor notes are being taken out of circulation in the next couple of months, replaced by newer, more secure versions. I'll admit I had completely missed this news.
Next year, the 100 and 500 kronor notes will be withdrawn, along with the coins.
I looked at my cash (as I said recently, Sweden is pretty cashless already) and found some old bills. I'll be spending them them in advance of the changeover!