An insurer will be letting holders of a variable annuity contract lock in account gains more often.

The Wellesley, Mass., U.S. arm of Sun Life Financial Inc., Toronto, says it will be changing the step-up feature in its Secured Returns for Life Plus benefit every year.

Sun Life sells the Secured Returns guaranteed minimum withdrawal benefit to purchasers of its Sun Life Financial Masters variable annuity.

In the past, owners of the Financial Masters annuity who bought the withdrawal guarantee could lock in gains only once every 3 years.

The step-up feature is available at no extra cost to customers who buy the Secured Returns benefit, Sun Life says.

The cost of the Secured Returns benefit amounts to 0.5% of contract assets.

Sun Life introduced the benefit in May. The annual step-up feature is available to existing clients as well as to new Secured Returns purchasers, Sun Life says.