The new development comes barely a month after unveiling of KCSE and KCPE timetables.
The ban means that candidates, who may have not validated their data by the end of this week (Friday), will not sit the examinations slated for October and November 2018.
Equally, the Head teachers of respective schools will also be punished by their employer for such mistakes.
“Due to the threat of breach of security occasioned by the photocopying of examination papers, Knec is committed to ensuring clean registration data for the accurate packing of materials.
"On account of this, under protest cases will not be accepted. Only subjects captured in the nominal rolls will be offered to the candidate,” KNEC has said in a circular dated April, 12.
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The circular has been signed by the Knec Chief Executive Mercy Karogo and her Teachers Service Commission counterpart, Ms Nancy Macharia, addressed to education officials and school heads reads.
“Heads of institutions should take note that they will be held responsible and surcharged for errors in the registration data for the 2018 Kenya Certificate of Primary Education and Kenya Certificate of Secondary Education examination candidates.”
As at this week, a total of 1,060,787 candidates had been registered for the KCPE exam, while some 663,811 will sit the KCSE test papers at the end of the year.
Last year, the question papers and answer booklets were combined to beat new cheats after it emerged that providing them separately led to collusion in some instances.
The pictures of candidates and their names are also printed on the papers to eliminate impersonation.
The circular points out problems experienced during the registration of KCPE and KCSE examination candidates in February.
“Most new schools wishing to be registered as Knec examination centres did not submit documents a year earlier as required, while many non-formal centres, especially in Nairobi, did not have registration certificates and could not be considered as Knec examination centres,” the circular reads.
It adds that some places in the Knec data base, which ceased to be examination centres due to inability to raise the required number of candidates, presented expired provisional certificates.
“Some candidates were not registered on time due to lack of birth certificates.
"Some new sub-counties did not submit the request for coding of examination centres on time. This led to schools registering using their old codes,” the two officials said.
Other challenges included failure to observe deadlines for the submission of nominal rolls by schools and unregistered centres lacking places to host them.
“The other [challenges] were candidates requesting for name, year of birth and gender amendments in the KCSE examination registration without amending the KCPE details first, and candidates who repeated in lower classes being declared as repeaters yet they have never sat the KCSE exam. This has affected the certification of such candidates,” the circular adds.