Different types of retirement plans have their contributions and distributions treated differently in Massachusetts. To prevent double taxation, Massachusetts allows a tax deduction for IRA distributions up to the total amount of alreadytaxed contributions.The Pension Service will help you design a 401(k) Program that your employees can easily understand and feel confident participating in. Set aside money towards their retirement. The CORE Plan is a 401(k) retirement planning solution that leverages the knowledge and best practices used today in many large retirement plans. Commonwealth's 403(b) Plan gives participants the opportunity to supplement your core retirement benefits. The Massachusetts Defined Contribution CORE Plan (CORE Plan) is a powerful tool to help your employees reach their retirement goals. This 10-year total can be reached through regular work with any MA contributory retirement system or through completing another service purchase2. The Massachusetts Defined Contribution CORE Plan is a multiple employer, 401(k) retirement program for non-profit organizations with 20 employees or less. There are two distinct types of retirement plans and it is mandatory you enroll in one.