The ISWC (International Standard Musical Work Code) is an internationally recognised reference number for the identification of musical works.
The ISRC (International Standard Recording Code) is an internationally recognised reference number to identify recorded music tracks and music videos. Each ISRC code identifies a specific unique recording and can be permanently encoded into a product as a kind of digital fingerprint.
Your song will be assigned an ISWC by the relevant royalty collection society (PRS for Music in the UK) when it is correctly registered.
PPL are the sole appointed agency for generating ISRCs in the UK. The recording will be assigned a code at the point of registration.