The S&P/ASX 200 Index (ASX: XJO) is under pressure on Tuesday and dropping into the red despite a strong session in the resources sector. At the time of writing, the benchmark index is down 0.4% to 8,387.8 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

ANZ Group Holdings Ltd (ASX: ANZ)

The ANZ share price is down a further 2% to $29.50. Investors have been selling this banking giant's shares this week after it announced the exit of its CEO, Shayne Elliott. Elliott is leaving in July next year and will be replaced by Nuno Matos on a $2.5 million a year deal. While the new CEO appears to be a great replacement, the market seems to have concerns over the timing of the change given that ANZ has just completed the acquisition of Suncorp Bank for $4.9 billion.

Perpetual Ltd (ASX: PPT)

The Perpetual share price is down 5.5% to $20.67. This morning, this financial services company was dealt a major blow by the Australian Taxation Office (ATO). Perpetual revealed that the cash returns from the proposed $2.175 billion sale of its Wealth Management and Corporate Trust businesses to KKR will be fully taxable. This means that the estimated cash proceeds to shareholders from the transaction would reduce from between $8.38 and $9.82 per share to just $5.74 to $6.42 per share. Management said: "Perpetual is extremely disappointed and disagrees with the Commissioner's views. Based on strong advice from relevant tax experts, including Senior Counsel, and following extensive Board testing and consideration, Perpetual continues to be of the view that the provisions should not apply." There are concerns that this could scupper the deal.

Premier Investments Limited (ASX: PMV)

The Premier Investments share price is down 4.5% to $34.68. This has been driven by a combination of market weakness and the retail conglomerate's shares going ex-dividend this morning. In September, the company released its full year results and declared a record fully franked final dividend of 70 cents per share. This was up 16.7% year on year. Eligible shareholders can look forward to receiving this on 8 January.

Pro Medicus Limited (ASX: PME)

The Pro Medicus share price is down almost 9% to $245.20. Investors have been selling this high-flying health imaging technology company's shares amid a selloff in the tech sector today. The selling has been so bad that the information technology sector is down almost 4% at the time of writing. It remains unclear what sparked the selloff, though profit taking appears quite likely.