Area homeowners -- including at least 15 in Arlington -- have been hit with notices of delinquent property taxes and in some cases liens on their property because the mortgage company responsible for paying the taxes failed to do so.

But the mortgage company says the payment problem is merely a massive computer error, which is being corrected and that homeowners should not be concerned either about the taxes or their property. The number of other homeowners affected in the area could not be determined this week.

New York Guardian Mortgage Co. in September switched from a simple computer system to a complex one that is designed to make automatic tax and insurance payments for about 50,000 homeowners in different parts of the country, said Gerald H. Bodell, chief operating officer of the mortgage company.

The problem caught the attention of the Arlington Office of Consumer Affairs after it received a complaint from one homeowner and then determined that several others in the county were affected as well. When the office received no explanation from the company on the delinquency, it requested an investigation by the New York attorney general's office.

It was December when the company realized there were programming errors in the system, because it started receiving "massive notifications" from local authorities about unpaid taxes, Bodell said.

The firm is gradually clearing out the problem accounts as they become apparent, and "the whole problem will be cleared up by June," he said. Any late fees or penalties will be paid by the mortgage company, not charged to the homeowners account, he added.

There could be problems with as many as 4,000 mortgages nationwide, but there probably delinquencies on no more than about 300, he added.

There may be more than the known 15 mortgages in Arlington County held by New York Guardian that are delinquent in property taxes, said to Jean D. Galloway, Arlington County director of consumer affairs.

Most of these appear to have been held formerly by Pioneer Mortgage Co. of Springfield, which sold a number of its mortgages to New York Guardian. The mortgage portfolio Pioneer sold includes properties in Virginia, Maryland and the District.

Neither New York Guardian nor Pioneer could say immediately just how many mortgages throughout this area might be affected.

Galloway wrote to Melvin Leventhal, New York assistant attorney general for consumer frauds and protection, asking for an investigation into the matter. The request was promted by one Arlington County home owner who received a notice that he was delinquent on his Arlington property taxes though his escrow account records showed he had more than double the amount due in reserve. She had first called the mortgage company but received no reply or explanation of the failure to pay, Galloway said.

Jacky Legrand, an employe at Maison des Crepes, said he was notified at the end of January that Arlington County property taxes of $650 for the second half of 1981, due in October, had not been paid. As a result, a lien was placed on his property. A property lien is automatic when taxes are not paid in Arlington, according to the county treasurer's office.

Legrand says at the time he received the notification he had more than $1,400 in his escrow account with New York Guardian. He called the mortgage company repeatedly and sent the firm a registered letter describing his problem, but never received a reply or explanation of what had happened, he said.

New York Guardian's Bodell said the company's records now show that Legrand's property taxes were paid on March 2. The treasurers' office by March 10 had no record of having received it, however.

Galloway says that she has received no reply or explanation from New York Guardian despite a Feb. 16 letter to the company. When she called the company earlier, she was told the matter would be looked into, but she was not contacted again, she said.

Bodell told a reporter he would try to pull out the mortgage records for Arlington County residents and write each of them a letter of explanation. This is what the company did when all the mortgages in an entire county in Nebraska went off the files in the new system, he said.

Most of the loans the company has made are FHA- or VA-insured, and the Department of Housing and Urban Development has contacted them on delinquent payments on these loans and is watching the correction process carefully, Bodell indicated. The state banking commissioner is aware of the problem as well, he said.

"We have made an error, and we are rectifying it, at great cost to us," he said.