In most of the country, 1981 will mark the first time in almost half a century that Americans will have the convenience and advantage of one-stop, one-step saving and checking.Starting Dec. 31, commercial banks and savings institutions will be authorized to pay up to 5 1/4 percent interest on checking accounts.

The exception is the Northeast, where Interest-bearing accounts have been legal for several years.In the six New England states plus New York and New Jersey, consumers now hold about $9 billion in these accounts. Ralph Kimball, assistant vice president of the Federal Reserve Bank of Boston, who has followed the New England experience since its inception, predicts that within five years half the checking funds in the country will be earning interest.

Although financial institutions assigns different names to interest-bearing checking accounts, they generally are referred to as NOW accounts for Negotiable Order of Withdrawal. From the viewpoint of the customer -- which can be either an individual or nonprofit corporation -- a NOW looks and works exactly like a check, that is, a form of third-party payment.

Legally, a negotiable order of withdrawal is a draft on a savings account, whereas as check is a payment order on a demand account. "Demand" means the account holder can get access to his money on request. "Negotiable" refers to a financial institution's right to withhold payment of the funds for a stipulated period, say 30 or 60 days. In practice, this right never has been exercised by those offering NOW accounts; funds are made available immediately.

The legal nuance between a check and a negotiable order of withdrawal is necessitated by the Banking Act of 1933, which prohibits payment of interest on demand accounts, but not savings accounts. It was the act's silence on the subject of drafts on savings accounts that led to the creation of the NOW account a decade ago.

The father of NOW account, Ronald W. Haselton, 49, president of Consumers Savings Bank of Worcester, Mass., recounted in a interview how the concept was developed. One day in 1968 he overheard a customer asking a teller to withdraw money from her savings account. The teller asked whether she wanted cash or a counter check. The woman replied it made no difference, because she was just going across the street to the commercial bank to deposit the money in her checking account.

Haselton, whose banking experience included stints at Citibank and the first National Bank of Boston, mused on what he considered the inanity of that forced walk across the street. Why couldn't his customer take care of her business under his roof? Was there really any fundamental difference between a check on a commercial bank and the counterchecks or money orders with the third party as a payee that savings banks routinely issued?

Consumers' lawyer Warren Lane Had argued that never before had drafts been directly written on savings accounts. Haselton said he countered, "Why can't it be done?" In July 1970 Consumers filed an application to allow customers to write drafts on their savings accounts. The bank paid 5 1/4 percent and charged 15 cents per check.

Thus began a process that led to a revolution in consumer banking, Looking back on it, Haselton recalled that the legal research consumed much more time and effort than did pricing and marketing. There were many battles along the way: with the Massachusetts commissioner of banks, who refused the application, and with the Massachusetts Supreme Court, which approved it on May 2, 1972, after the judge ruled the NOW draft was a "distinction without a difference" from existing types of withdrawal.

And then there was opposition from commercial banks, which feared savings banks would take away their customers. Four or five commercial banks turned down Haselton's proposition to clear consumers' orders of withdrawal before one brave bank agreed, convinced the idea would go nowhere anyhow. Finally, on June 12, 1972, Haselton issued NOW account No. 1 to himself and No. 2 to Lane. He copyrighted the name Negotiable Order of Withdrawal, but it was with a resigned pride of authorship that he saw NOW become the generic term anyway for interest-on-checking accounts.

At the start Haselton found himself a pariah among bankers, who threw brickbats at him. it was many years later before bankers welcomed him as a guru on NOW accounts.

The concept spread rapidly througout Massachusetts and across the Border into New Hampshire in 1972. The Massachusetts bank lobby was unsuccessful in getting legislation passed to outlaw NOW accounts. By the next spring the fight had spread to the national level. One of the early backers of NOW accounts on Capitol Hill was Rep. John H. Rousselot (R-Calif.), who was primarily concerned that federal savings and loan associations should have the same power to offer NOW accounts as their competitors, state-chartered S&Ls.

Fearing NOWs would affect the earnings of commercial and mutual savings banks in Rhode Island, Rep. Fernand St Germain (D-R.I.) introduced legislation to abolish NOW accounts. But after a four months deadlock in conference, a bill wa passed the following August authorizing all depository institutions in the two states to offer the accounts.

Convinced as a result of the the limited two-state experiment that NOWs were popular and wouldn't break the banks, St Germain became an ardent advocate of NOWs. Still they faced opposition from the bank lobby, and national NOWs were defeated again in 1975. In 1978 New York and New Jersey NOWs were approved.

Meanwhile, in 1978 banks were authorized to offer automatic transfer service (ATS) to customers to shift funds from their savings accounts to their checking accounts without their having to request each transfer. The zero-balance ATS was forerunner of the NOW. But because it was rather complicated, involving two accounts, and because banks were reluctant to pay what amounted to interest on checking when they had no competition in the field from thrifts, ATS did not prove a smashing success.

Efforts to extend NOW accounts to banks and thrifts throughout the country foundered until NOWs became inextricably linked with reform of the banking system.As one veteran of the NOW wars recalled, the NOW idea was so controversial that the only way it could be passed was to link it to other essential legislation that Congress was under a court deadline to pass. Thus it became a pillar of the Depository Institutions Deregulation and Monetary Control Act, passed last March.

Now that the entire country is about to get NOW accounts, attention is focused on New England where it all began. By August of this year, 80 percent of the depository institutions in that area offered NOW accounts. Four out of five Massachusetts households had NOW accounts.

In an article for the New England Economic Review, Ralph Kimball reviewed the New England experience. Two-thirds of all personal checking balances were converted to NOWs, he found.

In Massachusetss and New Hampshire, Kimball wrote, "aggressive promotion of NOW accounts by thrift institutions in 1973-75 greatly affected the speed at which NOWs spread among commercial banks and the terms on which NOWs were offered." In the other New England states, acceptance was slower. Initially, the intense competition prompted thrifts in Massachusetts and New Hampshire to offer free NOW accounts with no minimum balance, no service charges and no restrictions on the number of checks written.

According to the Federal Reserve Bank of Boston, NOW accounts are estimated to have reduced pretax earnings at all commercial banks in those states by 11.3 percent in 1975. Later the thrifts started pricing their accounts so they would make a profit on them. However, a significatnt number still offer free NOWs.

When discussing the outlook for NOWs around the country, bankers invariably say that the New England experience was unique, and that it is not likely to be repeated throughout the country. Growth and penetration will be slower, they predict.

Kenneth E. Reich, staff vice president of the U.S. League of Savings Associations, said he expects between 70 percent and 90 percent of the savings and loans with more than $50 million in assets, representing 90 percent of the total assets in S&Ls, to offer NOW accounts in the 1981.

Cleveland S&Ls have banded together to finance an ad featuring puckered lips. The copy reads, "On Dec. 31 you can kiss your bank goodbye." However, no national advertising campaign is planned by the league to coax business away from banks. Moreover, Reich added he did not think NOW accounts would bring in sufficient new money to make any difference in the currently unhappy financial condition of thrifts.

Patrick J. Lawler of the Federal Reserve Bank of Dallas does not predict much competition from thrifts. Noting that NOW accounts may become even more popular in the Southwest than they were in New England, he warned, "Since checking accounts appear to be so lucrative in this [federal Reserve] District, banks here have more to lose than those in New England if thrifts win away their customers. But if banks retain customers by paying interest and lowering service charges, that will cost profits too."