What Do The First 2 Digits Of The Serial Number Stand For ?

Excluding the 1992 $5, the 1988 $10 and all paper notes, it stands for the year.

They are just serial numbers as in Canadian currency and stand for nothing else Baanos.

In 1988 & 1992 the prefixes had no real relevance apart from differentiating the notes from each other.

My belief is that perhaps the AB letters represented "Australian Bicentenary". At this point there would have been 24 notes per sheet prior to cutting. Hence AB10-AB33 (24 individual prefixes) & the second run was AB10-AB57 (which would be 2 runs of 24 individual prefixes - 2 x 24). Also there were sheets of 24 notes (12's & 4's) sold to collectors, staff & dealers. The presentation folders also existed in AA00-AA23 (24 individual prefixes). As for those prefixes, they were differentiated with the best way to start the series with AA.

The $5 notes were released in polymer in 1992 obviously without enough thought about the future. Maybe they were just too excited. So the original notes were a paler colour. The serial numbers started at AA00 to AB19 (runs of 40 notes, which means 3 runs made up the 120 prefixes).

Then came the smart move...in 1993. I believe it represented a better approach to the banknotes of the time. The worlds most secure notes needed to stay secure, well if you think that the same signatories were to be on many consecutive years of notes. I believe this is what led to the BA prefix in the $5 denomination. One because they didn't want the AA prefix appearing again because of the possible future legalities & confusion behind it.

So every year from then on had the two letter prefix, followed by the two digit year & then the serial number.

From 1993 through to 1996 saw a release of a new note each year.
1992 - e.g AA? ****** Paler $5 (24 per print run)
1993 - e.g AA93 ****** $10 (45 per print run) & e.g BA93 ****** Revamped $5 (40 per print run)
1994 - e.g AA94 ****** $20 (40 per print run)
1995 - e.g AA95 ****** $50 (40 per print run)
1996 - e.g AA96 ****** $100 (32 per print run)

So if a note is printed this year, the first prefix will take on AA12 ******

? - denotes any number & * - denotes any serial number

The prefixes for the $5 were BA - BM, CA - CM, etc.
The prefixes for the $10, $20, $50 & $100 were AA - AM, BA - BM, etc.

Example:
AA, AB, AC, AD, AE, AF, AG, AH, AI, AJ, AK, AL & AM
& then obviously first letter would change to B, C, D, E & etc.

Thank you all. I appreciate this very informative answer goatieman23.