Over 15 per cent of second level students made errors when filling out their Central Applications Office form this year.
Some students put down the wrong sex, date of birth or home address, according to a CAO spokesman. The most common mistake was applying for courses which did not exist.
Almost 10,000 students made at least one error in their form. About half of these incorrectly put degree courses in the certificate/diploma list and vice versa. About 1,600 students applied for courses which had been cancelled and 8,691 applied for courses which did not exist.
The rate of mistakes was almost as bad as last year, although the introduction of online applications reduced it by a small margin.
The CAO spokesman said none of this year's errors would have been made if students had applied online.
"In fact, if parents want the students to avoid errors in course codes, they should encourage the students to use the online application system.
"If they apply online and enter an incorrect code the computer will simply stop them immediately and will allow them to proceed only when they have entered codes correctly," he said.
The CAO also does not advise those who have made mistakes to blame their career guidance teacher. It says these teachers have no responsibility for the way applicants complete the form.
A spokesman said: "Surely any young person who aspires to third level education should be capable of completing correctly a simple form."
The CAO is currently trying to get as many students as possible to use the online service, which is available at www.cao.ie.
While the service has proved popular, students have had to pay their application fee through a bank. In future it is likely students and their parents will be able to pay online, probably with a credit card.
The CAO has just sent all applicants their statement of course choices. If students notice a mistake relating to a restricted application course they must reply to the CAO within seven days to have it changed. This rule also applies to mature students.
Other applicants can wait until May when CAO sends out a change-of-mind form which they use to amend their choices.