Once you have been accepted by the college you can defer - you DO NOT need to reapply through CAO the following year. However you do need to be very careful of how you accept your place - it is different for deferred entrants than for normal ones. In short, this is what happens:
On receipt of the offer notice:
1. Do not accept the offer in the manner shown on the Offer Notice.
2. Write immediately to the Admissions Office of the appropriate higher education institution (UL for you) setting out the reason(s) for the request. Mark “DEFERRED ENTRY” clearly on the envelope.
3. The appropriate part of the Offer Notice must be attached to the letter, i.e that part of the notice which shows the offer you wish to be deferred.
4. The letter must arrive in the Admissions Office at least two days before the “Reply Date” shown on the offer notice.
5. The HEI (ie UL) will communicate the decision to the applicant. If the deferral is not granted, you may still accept the offer for the current year.
6. All communications about deferral must go to the Admissions Offices and not to CAO.
In order to take up the deferred place, the applicant must reapply through the CAO in the succeeding year, paying the appropriate application fee, and placing the deferred course as the only preference on the Application Form.
When reapplying the following year you must complete an application fully. In other words, you must include again any documentation, if any were needed, which you provided with the original application. (ie keep copies of everything you send and send them again the following year).
Page 5 of the CAO handbook axplains how to defer in detail (link below if you can't find yours).