It's never too soon to start saving for 'leisure years'

The time to begin planning your retirement is: (A) three years before retirement, (B) 10 years before, (C) 15 years before, (D) as soon as you start working.

The answer could be all of the above, depending on what is meant by planning. But if it means beginning a savings program that will provide a nice nest egg at retirement, the answer is D, when an individual retirement account (IRA) or salary reduction plan - known as a 401(k) - can be opened.

Beyond savings, however, retirement planning involves many decisions about what people want to do, where they want to live, their interests, hobbies, recre-ational activities, and family cir-cumstances.

Not too long ago, people were left to figure these things out for themselves. Shortly before retirement, the employees would be called into the personnel offices and given the standard details about what they could expect from the company retirement program and social security. From there, they would be led to the retirement party and, then, out the door.

While that is still the case at many firms, a growing number of more enlightened companies are offering workers and their spouses many hours of pre-retirement counseling spread over several months before the last working day. Using both inside and outside experts, these seminars cover such topics as financial planning, taxes, legal matters, deciding where to live, and post-retirement careers or part-time jobs.

At the Polariod Corporation in Cambridge, Mass., employees who are nearing the end of their careers and considering early retirement can sometimes even take a retirement ''rehearsal'' of three months unpaid leave. If they feel they're not ready or don't like retirement, they can come back; if they're enjoying the leisurely life, they can stay out and become officially retired.

Still, even the most extensive company pre-retirement counseling cannot make people's decisions for them.

''The individual is a key player here, and they can be coached to take action ,'' said George Barbee, executive director of the Consumer Financial Institute, a planning firm in Newton, Mass. ''But he has to take that action to become self-reliant.''

One of the first steps to concrete retirement planning is to take a good look at current expenditures - the amount of money needed to maintain current standards of living. This includes food, clothing, housing, utilities, transportation, health care, and insurance. It also includes what is commonly known as discretionary expenses, such as recreation, vacations, entertainment, gifts, and charitable contributions.

Next, compare these costs with what you will need at retirement. Your home may be paid off (or you may pay it off with part of your retirement nest egg). Costs for business clothes and commuting will drop, but vacation expenses will likely go up. Some taxes will probably go down, but probably not property taxes, assuming you keep the home you had before retirement.

Inflation, of course, has to be factored into these expenses. While a working person can depend on cost-of-living adjustments and merit pay increases to help keep pace with inflation, most of these adjustments disappear at retirement. For example, people with $50,000 in current annual expenses and 10 years until retirement can expect to need $89,500 a year when they leave work, if inflation averages 6 percent a year, according to Touche Ross & Co., the accounting firm.

It is possible to get the extra money together if you begin planning for it soon enough, Touche Ross says. Say you estimate your pretax needs will exceed your sources of income by $1,000 a month, or $12,000 a year. A fund of $120,000 earning 10 percent would provide that $12,000. If you had 10 years to put the $ 120,000 together, you would need to invest about $7,500 a year in each of those years at a 10 percent rate of return.

Another major decision that must be made by people who are about to retire concerns their homes. Sure, you can sell your home and legally avoid paying capital-gains taxes on up to $125,000 of the sale price after age 55, but there are other things to consider. The emotional and family ties connected with a home may be too strong for either the husband or wife to sell it now. Many couples, having sold their homes and moved to ''retirement communities,'' have come to regret the move and to wish they could have their old houses back.

One way to avoid this problem might be to rent your house for several months while you rent an apartment or condomunium in some place like Florida or Arizona. If you like the new area, you can stay, or you can reclaim the old homestead.