A bar of soap is typically good for three years from the manufacturing date. Some signs that soap is starting to go bad include visible cracks and dryness.
Manufacturers often print expiration dates allowing 6 months before the soap actually expires, so that people are not at risk of ineffective soap and to encourage more soap sales. The FDA does not require companies to print expiration dates on packaging other than drugs, and soap does not always have a printed expiration date. To keep bar soap fresh longer, store it in a cool and dry place away from sunlight and air.