"Our last splurge," Phyllis Deuel said as she guided her two children out of the Sears, Roebuck & Co. store in Arlington, where she had just charged $40 worth of merchandise.

"An Easter suit for him," she said, pointing to her 6-year-old son Kenneth. "And some draperies I had ordered for the house."

Deuel said the family will have to charge less in the future if Sears carries out plans to raise monthly minimum payments on charge accounts. After the Deuels pay their mortgage and buy groceries with the paycheck that the elder Kenneth Deuel brings home from his job with the U.S. Postal Service, there is not enough left to cover higher monthly charge account payments, she said.

The only solution, she said, is to keep monthly payments down by charging less and maintaining a lower charge account balance.

Deuel and her family are among the thousands -- perhaps millions -- of consumers across the country who will have to adjust their budgets so they can afford the higher costs of credit triggered by President Carter's proposals to restrict consumer charges and loans.

Federal Reserve officials have told businesses that they must determine their outstanding customer credit balances as of March 14. Fifteen percent of future credit charges that exceed that day's balances must be deposited in noninterest bearing accounts with the Federal Reserve.

To comply with the requirements, businesses have said they will raise monthly minimum payments, restrict new credit and lower existing credit ceilings. Sears, for example, announced that it will raise monthly payments by as much as 25 percent.

In addition, bank cards such as Visa and Master Charge are considering a membership fee if legal prohibitions are removed.

Federal Reserve Board officials said last week that businesses must give 30 days' notice to customers before raising monthly payments on charge accounts. The board also said that companies must allow consumers to pay off their existing balances under terms in effect at the time of the purchases. However, new credit terms and higher rates may be applied to accounts if customers make any new charges.

The government proposals have been assailed by critics who contend that they would hurt small consumers without appreciably helping the economy. The proposals would affect only about 15 percent of the nation's total consumer debt; the curbs on credit cards would touch only about 4.5 percent of consumer debt, according to Federal Reserve figures.

The possibility that some businesses may raise interest rates on customer accounts rankled some shoppers -- even those who said they pay their balance each month in full before a finance fee can be imposed.

Jim Brooks, who works at the Pentagon, explained why as he walked through the Sears parking lot:

"If I signed an application for credit that provided for 18 percent interest and then they told me it would be 22 percent . . . well, I'd tell them what they could do with it."

Consumer leaders, including Kathleen O'Reilly of the Consumer Federation of America and Sandra L. Willett of the National Consumers League, expressed concern that the small consumer may be trampled as businessmen rush to comply with government rules.

"The man with the $2,000 line of credit won't be affected by this," O'Reilly said.

Willett predicted that the credit strings will bring prosperity to at least one group. "It will mean a growth in business for debt collectors," she said, because many consumers already living on the economic edge will not be able to pay the increased credit costs.

Industry statistics and academic surveys have not projected the full impact of credit controls on consumer spending. Nor have they yet assessed the hardships that could result for individuals.

A review of consumer bill payment records suggests that the stereotype of the consumer as an overextended credit card addict, fueling the nation's inflation, is not entirely justified.

For instance:

More than half of the charges that consumers make on their credit cards are prepaid immediately. Of the $27.8 billion charged last year on 41 million Visa accounts, cardholders paid finance charges on only $13 billion. The other $14.8 billion was repaid before Visa could assess any finance charges.

Delinquencies charged off due to bankruptcy, death or other reasons represented 1 percent of credit cards sales last year on Visa accounts.

Credit card holders on average, use less than 50 percent of their credit ceiling. The average outstanding balance on a Visa account on Dec. 31, 1979, was $501, while the average credit ceiling allowed was about $1,035.

About 57 percent of department store sales for chains such as Sears are purchased on credit. Customers pay cash for the other 43 percent.

The size of consumer credit spending shrinks even more when compared with the nation's total debt. William Dunkelberg, associate professor of economics at Purdue University and associate director of the university's Credit Research Center, estimates that consumer credit card charges now total about $60 billion -- or about 1.5 percent of the combined $4 trillion indebtedness for government, business and consumers.

At the end on 1979, consumer debts totaled $1.225 trillion, Federal Reserve figures show. That consisted of these components:

$844 billion for household mortgages.

$311 billion for consumer credit installments, including $115 billion for automobiles, $17.4 billion for mobile homes, $29 billion for banks credit cards and overdraft plans, $22 billion for retail credit cards, $4 billion for gasoline credit cards and $123.3 billion for home improvement loan installments, appliance loans and personal cash loans.

$70 billion for noninstallment credit, such as consumer charges on travel and entertainment cards like American Express.

The president's credit control restrictions apply only to a selected portion of that $1.225 trillion bill. Household mortgages, automobile loans, mobile home loans are not affected by the new proposals. Portions of noninstallment credit and of the miscellaneous installment credit category also are excluded.