The TickIT scheme has ended and, with effect from 30 November 2014, certifications to ISO 9001/TickIT are only valid for the underlying ISO 9001 requirements.
TickITplus is the successor scheme; for more information about TickITplus, please go to www.tickitplus.org.
All requirements of ISO 9001 still apply as ISO 9001 is the certification standard behind TickIT. The requirements of ISO 9001 are very generic and the benefit of TickIT was that the TickIT Guide provided appropriate interpretations for the software development sector and had to be assessed by specially qualified Auditors with proven understanding of developing software.
So when the scheme finished, the difference is that the auditor used may not be a qualified TickIT Auditor, but has to be deemed competent by the certification body to audit software activities. From a purchaser of software perspective, there is a low risk (that increases over time), that a company (particularly one that does not produce software as its main product) will have a lower level of assurance as the auditors used are less qualified, resulting in the potential for lower product quality.
TickITplus has both a competency framework and process conformity requirements over and above what ISO 9001 requires, making it a better model for maintaining and improving product quality.