Up to about four or so years ago, till receipts were printed on special paper and were not able to be recycled. Remember when till receipts were on shiny paper?
Thanks to the pressure to recycle, supermarkets and other retailers changed to printing on ordinary paper so now all till receipts can be recycled. Also, the smallest supermarket till receipt has been designed so that it is large enough to be recycled, in case you ever wondered why you get such a big piece of paper when buying one item!
This has now become a good approximate measure. If a piece of paper or cardboard is smaller than a supermarket till receipt for one item, then it is too small to be recycled and should be treated like shredded paper and put into your black top rubbish kerbside bin. Use this as a size guide to what paper and cardboard can go into your blue top kerbside recycling bin.