Your income and outgo are perilously close, you don't have enough cash reserves to warrant the services of a financial planner, but you need help.

Many Americans are turning to personal finance software programs for use with their home computers. "Financial planning and money management programs are among the fastest growing categories in the software industry," says Ken Wasch, executive director of the Washington-based Software Publishers Association.

The services offered in such programs are many and varied but they come down to three basic functions:

*Electronic checkbook. Organizes, categorizes and records check and credit-card transaction, calculates balances and writes checks.

*Financial statement, Calculates net worth, with lists comparing assets and liabilities, income and expenses.

*Budget preparation. Allows creation of budget categories and compares them to actual expenditures on daily, weekly, monthly or annual bases.

The more sophisticated programs-such as Andrew Tobias' "Managing Your Money," John Reese's "Dollars and Sense" and Sylvia Porter's "Your Personal Financial Planner"-also provide income tax and insurance preparation and advice, portfolio management, short-and long-term financial planning, loan amortization, college expense analysis, retirement planning and more.

Reese's "Dollars and Sense" ($120-$180 retail, depending on the computer system) for example, is a program designed for the home and small business. It will handle 120 main accounts, 12 separate checking accounts and up to 4,000 individual transactions on a double-sided floppy disk.

Setting Tobias' program ("Managing Your Money," $200 retail, Micro Education Corp. of America), apart from the others: a crisp, light sense of humor. In explaining how to set up a business affairs disk, for example, Tobias suggests naming it mybidness "unless you come from Texas, in which case it's mybidness."

Software experts suggest consumers interested in personal finance packages shop around for the software program that comes closest to meeting their specific needs and at the best price. Cheap software may mean poor quality and limited features. Consumers should ask for thorough demonstrations of different financial programs' capabilities . . . and then try to find out which ones are used by the savviest professional planners.