what is the digital object identifier or doi
Digital object identifier In computing, a Digital Object Identifier or DOI is a persistent identifier or handle used to uniquely identify objects, standardized by the International Organization for Standardization (ISO).[1] An implementation of the Handle System,[2][3] DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports and data sets, and official publications though they also have been used to identify other types of information resources, such as commercial videos.
P45 (tax) The "P" code refers to documents in the PAYE series, in the same way that self-assessment documents are prefixed "SA" (e.g., SA100 - Individual tax return) and Tax credits paperwork is prefixed "TC" (e.g., TC600 - Tax credits application).[citation needed]