The scheme is based on unique Permanent Retirement Account Number (PRAN) which is allotted to each Subscriber upon joining. Subscriber contributes towards NPS (directly or through the Employer he/she is working with) during his/her working life. On retirement or exit from the scheme, the Corpus is made available to him/her with the mandate that some portion of the Corpus must be invested in to Annuity to provide a monthly pension post retirement or exit from the scheme.