Canadians are being offered a record 19 1/2 percent interest on Canada Savings Bonds for the year beginning Nov. 1, Finance Minister Alan MacEachen announced today.

The government also is raising the interest on about $14.4 billion of existing savings bonds to the same rate for the next year.

Rapidly rising interest rates during the latest year have caused Canadians to cash in massive amounts of the bonds. The savings bonds issued by the government are unique instruments that can be cashed in on any business day for their full face amounts plus accrued interest.

The rates offered in the 1981-82 campaign are about three times that available on U.S. savings bonds. But Canada Savings Bonds are available only to Canadians.

They are the most widely held investment instrument in Canada and, while $3.3 billion in bonds were sold in last year's campaign, some $2 billion worth were cashed in, reducing the net amount raised to $1.3 billion.

Of that amount, $850 million was raised through payroll savings plans, indicating that investors generally were rejecting the savings bonds.

Currently, all Canada Savings Bonds pay 18 1/2 percent interest. A year ago the rate was 10 1/2 percent on older bonds.

To slow the cashing in of bonds, the government raised rates payable on existing bonds four times in the past year.

The new bond series has a seven-year term until they are due. The interest rate on the second through seventh year is 10 1/2 percent, but MacEachen said the rate will be reviewed annually.

The savings bonds represented as much as 40 percent of Canada's federal debt as recently as 1975. But because they can be cashed in at any time, the government decided to de-emphasize the bonds as a source of funds. Currently the bonds represent less than 20 percent of Canada's $85 billion federal debt.

Some of the reduction is due to investors cashing in the bonds, but at the same time the total of Treasury bills outstanding and of other government bonds has increased.

In the latest year, Treasury bills outstanding rose about $4 billion to about $23 billion. Other government bond and debt obligations total around $45 billion.