Update: I read this as 90 day report, not extension, but same thing. You can choose different types of appointments on the website, so I believe there’s also a selection for extensions
You can book an appointment on this website for your 90 day report:
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It’s super easy and then you just show up 15 minutes before your appointment. You go directly into immigration and to the counter it says on your ticket - don’t have to wait in lines or wait for a queue. My family has done it several times and we’ve only been in immigration at our appointment for maybe 10-15 minutes. So quick and easy (as long as you have all the correct paperwork).
The appointments open about 3 weeks in advance, so keep checking and about 3 weeks from the day you want to go, get on and book an appointment before they all go quick. I will say every time there’s been a glitch in the system and my initial confirmation says the day before the day I selected for some reason, but then once everything is confirmed, the confirmation slips shows the day I selected. Hope that helps