the ruling regarding products that contain fat derived from animals which have have not been slaughtered as per the requirements of the shari'ah is that they are impure and haram, even if it may be fat from a goat or a cow. [see fatawa ridawiyyah 4/572]. nb Pig fat is intrinsically impure and haram. if it is added in a product then it is apparent that such a product is impure and haram. in the case of the £5 notes, the following points need to be considered in order to come to a judgment. we do not consume the notes nor do we use them as a cosmetic. they are not liquid or moist so the impurity cannot spread onto another item, such as clothing. however, where it is an issue of concern is having the note(s) in your pocket while praying salah. a similar example regarding having an impure item in one's pocket can be seen in the books of fiqh: the ruling regarding having a bottle in one's pocket which is filled with blood, urine or alcohol. the jurists have ruled that the salah will not count [see bahar e shariah, chapter of impurities, vol 2]. based on this, the ruling seems to be clear - having the new £5 note in one's pocket while praying salah would render the salah void. however, what must be considered is the general usage of notes. notes are used on a day-to-day basis and are common need. the notes may fall under the category of hajat, in that though the notes are possible to live without, it is very difficult to and is a reason for hardship [for the definition of hajat, see fatawa ridawiyyah 21/205]. keeping in mind the following principles: - necessity permits carrying out prohibitions - hardships bring ease [see al-ashbah] also, everyone is involved in keeping and taking such notes, so umum al-balwa needs to be considered here too, which could perhaps lighten the ruling. umum al-balwa is from the causes that lighten the ruling, especially when it concerns cleanliness [taharah] and impurities [najasah]. [see fatawa ridawiyyah 4/381-382;4/390] the ruling regarding the general handling of the notes could also fall under the categories mentioned above. nonetheless, to pass a fatwa on this issue and ultimately provide the ruling is the job of a qualified mufti, and therefore an istifta should be sent to a reputable dar al-ifta. wa'Allahu ta'ala a'lam.