The company announced last month that users aged 13 to 15 would start receiving notifications that their accounts would be deactivated from 4 December.
An estimated 150,000 Facebook accounts and 350,000 Instagram accounts are expected to be affected. Threads, which operates similarly to X, requires an Instagram account for access.
Australia’s pioneering social media ban takes effect on 10 December. Companies that fail to take “reasonable steps” to prevent under-16s from holding accounts could face fines of up to A$49.5 million (US$33 million, £25 million).
A spokesperson for Meta told the BBC on Thursday that "compliance with the law will be an ongoing and multi-layered process".
"While Meta is committed to complying with the law, we believe a more effective, standardised, and privacy-preserving approach is needed," she said.
The government should require app stores to verify the age of users when they download apps and ask for parental approval for under-16s, Meta said, as this would eliminate the need for teens to verify their age across different apps.
Last month, Meta said users it had identified as under 16 would be able to download and save their posts, videos and messages before their accounts are deactivated.
Teens who believe they have been wrongly categorised as under 16 can ask for a review and submit a "video selfie" to verify their age. They can also provide a driver's licence or a government-issued identification.
Alongside Meta's three platforms, the other social media sites affected by the ban are YouTube, X, TikTok, Snapchat, Reddit, Kick and Twitch.
The government says the ban is aimed at protecting children from the harms of social media but critics say the move may isolate certain groups who depend on platforms for connection and push children to less-regulated corners of the internet.
