The average annual return on one-year Treasury bills dipped again yesterday to 12.173 percent, down from 12.194 percent last month. It marked the lowest level since November 1981, when the yield was 10.506 percent.

The return on tax exempt All Savers certificates slipped to 9.85 percent, down from the current 9.87 percent. The new rate goes into effect Sunday where banks and savings and loans are open and Monday here. The return is based on 70 percent of the average annual investment yield on one-year Treasury bills, which reached 14.07 at yesterday's auction.

At the new rate, it will take an investment of $10,152 for one year to earn $1,000 in interest. This is the maximum amount an individual can earn tax free on federal returns on this investment; married couples filing jointly can take an exemption of $2,000 on double the amount invested. This is a one-time exemption during the time in which All Savers certificates are sold, between Oct.1, 1981, and Dec. 31, 1982.

Savings and loans, which have captured nearly two thirds of the dollars put into All Savers certificates, are lobbying hard to extend the deadline beyond the end of this year. According to the Federal Reserve, the amount of money in these accounts at commercial banks was $21.3 billion at the end of the first quarter of this year.