An insurer says it will pay a bonus of either 6% or 7% to purchasers of a new annuity contract.

The Wellesley, Mass., U.S. division of Sun Life Financial Inc., Toronto, will be tying policyholder returns on the new SunDex Bonus Fixed Index Annuity to growth in the S&P 500 stock index.

Buyers will get a bonus of 6% for premium payments under $250,000 and 7% for premium payments equal to or greater than $250,000, Sun Life says.

Sun Life will add the bonus to the contract account value immediately, and the bonus will vest fully after 5 years, the company says.

Sun Life is selling the annuity along with an option to buy the InControl Lifetime Benefit, a feature that lets holders defer part or all of the annual withdrawals that the contract permits and store those withdrawals in the contract for future use, Sun Life says.

The contract comes with a 10-year surrender charge schedule.

Sun Life is writing the contract through Sun Life Assurance Company of Canada (U.S). Sun Life Assurance is responsible for backing the product guarantees.