Can someone please confirm how long the 800k in the bank for a retirement extension has to be in the bank before you can dip in to it down to 400k? Also when does it have to be topped up again to 800k before the next extension? Is it 2 months the same as with the 1st extension? Thanks.

800k or more for two months before your new extension and three months ago.

Draconian but thems the rules.

OP, it's 2 months in the bank prior to day of application. After which must be maintained at 800k + for next 3 months. 

After those 3 months it can be reduced to a minimum of 400k. Then topped up to 800k 2 months prior to date you attend for next extension.

 

Note. Many recommend to have a dedicated account for this. Keep your day to day banking separate. Not necessary but keeps things simple. 

Some people (myself and others) keep the balance 800k+ all year round. In that case some opt for FD account.