In an employee stock purchase plan (ESPP) that is tax-qualified under Internal Revenue Code Section 423, a lookback allows the purchase price (with or without a discount) to be based on the market price at either the beginning or the end of the purchase period, whichever price is lower (a typical purchase period runs for six months).

Example: In a plan with a lookback and a 15% discount, if the stock price is $10 at the beginning of the purchase period and goes up to $20 at the end, your purchase price is just $8.50 ($10 minus 15%).

The compound lookback is sometimes written look-back or look back.

For details on lookbacks and ESPPs in general, visit the ESPP section of this website.