Knight Capital Group Chief Executive Officer Thomas Joyce estimated last week’s trading loss will be $270 million after taxes and told clients the firm is “in good standing” with clearinghouses.

The post-tax loss compares with a previously disclosed pretax loss of $440 million. The letter comes a week after Knight, one of the biggest market-making firms in the US, was driven to the brink of bankruptcy after a technology malfunction spewed orders into the market by mistake. Joyce told clients that the company is in talks with outside advisers as it works to prevent another error.