Joint and several liability of partners: retiring partner remains liable until retirement date unless timely notice limits tax liability. Partners are jointly and severally liable for any tax, interest or penalty of the firm. A retiring partner remains liable for liabilities up to the date of retirement. The retiring partner or the firm must notify the Commissioner in writing; if notice is given within one month of retirement, the partner's liability is limited to liabilities up to the retirement date. If no timely notice is received, the retiring partner remains liable until the Commissioner receives the intimation.