NAB's cash earnings have fallen by 12.8% to $3.5 billion in the six months leading up to March.

CEO Andrew Irvine cites a competitive mortgage market and increased tax rates as primary reasons for the earnings drop.

The bank's net interest margin decreased to 1.7%, impacting overall profitability.

NAB is experiencing higher loan arrears and a downturn in its personal banking profitability.

In response, NAB has initiated a $1.5 billion share buyback and maintained an interim dividend of 84 cents a share.

While acknowledging economic challenges, Irvine remains optimistic about potential tax cuts and policy changes providing relief later in the year.

Analyst John Storey raises concerns about whether NAB's performance can continue to drive its share price upwards.