Because you are married, you cannot be treated as single. You can file a joint return, or you can opt to file as “married filing separately.” However, if spouses live apart and meet certain tests, one may qualify to file as head of household instead of married filing separately. To do this, you must have a qualifying person live with you (or a dependent parent even if not living with you); a spouse is not a qualifying person.
A retirement plan that meets tax law tests and allows for tax deferment and tax-free accumulation of income until benefits are withdrawn. Pension, profit-sharing, stock bonus, employee stock ownership, and Keogh plans and IRAs may be qualified plans.