AUSTRAC's conscise statement of claim outlines the magnitude of the theoretical maximum fine Westpac could face.

"Westpac has contravened the act on over 23 million occasions, each contravention attracting a civil penalty between $17 million and $21 million," the regulator noted.

Assuming 23 million contraventions at the lower end of those maximum penalties, that amounts to a potential maximum fine of $391 trillion.

As highlighted in the Commonwealth Bank money laundering case, the actual penalty paid is likely to be much smaller — CBA was facing a theoretical maximum penalty of close to $1 trillion, but ended up settling with AUSTRAC for $700 million in penalties for 53,700 breaches.