The firm admits 6,800 customers were mistakenly affected by a re-price undertaken in 2001 and 2002, with around 4,200 policies overstated and approximately 2,600 understated.
Standard Life spokesman Paul Keeble says that, in around half of the affected cases, the error is worth less than £25.
But he admits that, in some instances “the discrepancy was significant”.
The re-price required investments to be moved from what the firm calls series 1 funds to series 4 funds.
It claims it identified late in 2008 that a number of policies had residual investments in series 1 funds.
Keeble says: “As a result, the fund values have been incorrect. We clearly needed to correct customer records which we did in November 2008. This put customers back into the position they would have been in had the error not occurred.
“We obviously regret these errors have happened and we have put in place further controls and will continue to monitor and review our processes to reduce the likelihood of this happening again.”