On Monday (TD maturity date) a single credit transaction for the total amount due was shown in our cheque account. The time stamp was about 9:45 am.
On Tuesday morning four credits were shown: the two principal repayments and the two interest payments timestamped about midnight.
I expect if you looked at any BNZ customers TD maturing deposit account (after 10.00am) on maturity date you would see a single amount AND on the next business day you would see both a principal and Interest credit.
I guess BNZ must have a dual update process that posts transactions twice to accounts.
The first intraday online TD update must still have legacy code that accumulates credits posted at the same time. Back in 1970’s this logic was often used to reduce expensive disc storage costs.
(retired IT consultant).