From IRS, "It is important to understand that the K-1 reflects the S corporation's items of income, loss and deduction that are allocated to the shareholder for the year. It is not the corporation's responsibility to track a shareholder's stock and debt basis but rather it is the shareholder's responsibility".

See link: https://www.irs.gov/businesses/small-businesses-self-employed/s-corporation-stock-and-debt-basis