Christmas shopping by mail can save time, money and energy -- but only if the gifts you ordered arrive on time. When they don't, you need to know your basic consumer rights.

These are spelled out in the Federal Trade Commission's mail order rule, issued in 1975 to reduce complaints about delayed deliveries. One consumer summed it all up by telling the commission that it was "very disheartening to receive supposed Christmas presents ordered in September or October sometime around Easter."

Among the protections now afforded to those ordering merchandise from the $40-billion-a-year mail-order industry are the following:

* You must receive the merchandise when the company says you will. If the company doesn't specify a delivery time in its sales material -- such as "allow 5 to 6 weeks for delivery" -- the company must ship the goods within 30 days after receiving the order.

* You may cancel the order and receive a full refund when the company doesn't ship the merchandise within the 30 days or the specified delivery time. The company must mail the refund within seven business days after receiving your request.On a credit sale, the company must adjust your account within one billing cycle.

For Christmas shoppers the refund option can be a decided advantage. Suppose, for example, that you ordered a gift back in mid-November and now -- 30 days later -- it hasn't arrived. Instead, you have a notice from the company saying that delivery has been delayed until January. Under the federal rule, you can agree to the delay or you can ask for a refund. With the refund in hand or on the way, you can purchase a substitute gift to present in time for Christmas.

The rule doesn't cover all mail-order merchandise or transactions, however. Exceptions include mail-order photo-finishing, magazine subscriptions and other serial deliveries (except for the initial shipment), seeds and plants, collect-on-delivery (COD) orders and credit orders where the merchandise is mailed before the account is charged.

When you have a mail order problem, the FTC recommends that you first write to the company. If it isn't resolved, you can call the local or state consumer office in your area and in the area where the company is located, your local postmaster and the publication that carried the advertisement.

A copy of the correspondence should go to the FTC, which doesn't generally resolve individual disputes but does track complaints to see if these is a pattern of illegal practices. Companies that fail to comply with FTC rules are subject to civil penalties.

In addition, the Direct Mail/Marketing Association (DMMA), a trade group of 2,800 companies in the mail-order business, helps resolve consumer problems through its Mail Order Action Line, 6 East 43 St., New York, NY 10017.

DMMA also worked with the FTC to publish a free booklet of 10 tips for consumers ordering merchandise through the mail. "Mail Order Shopping" can be obtained by sending a stamped, self-addressed envelope to DMMA at the address listed above and asking for a copy of the booklet.

One tip suggests that consumers keep a record of their order, including the company's name, address and phone number; information about the item purchased, such as the catalogue number; the cancelled check or a copy of the money order and the date the order was mailed.

That record would help if the merchandise is late or lost and you need to file a claim for non-delivery.

Right now, the FTC is wading through 25,000 complaints from consumers who ordered merchandise earlier this year from SMM Mail Order Marketing Inc., a California mail-order company that filed for bankruptcy and left 65,000 pieces of merchandise in limbo.

The merchandise is wrapped, addressed and sitting in a Los Angeles warehouse awaiting shipment to consumers who already have paid for the goods. But there is no postage on the packages and the FTC estimates that $100,000 is needed to make the deliveries.

"The issue is where will the [postage] money come from," said FTC attorney George Schulman. He is now trying to work out a deal in bankruptcy court on postage so the packages can be mailed -- perhaps in time for Christmas.