I just checked my bottle Kikkoman in the fridge and it does have a "best if used by date".

If it were a few months past that date, I'd use it anyway. A few years, and I'd throw it out.
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I just asked by wife who buys soy sauce by the gallon. She says that it should be fine.
Source(s):
wife

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It is safe to use the soy sauce. The sodium from the sauce will prevent anything from growing. The flavors may fade after the expiration date but you need not worry about getting sick from illness causing microbes.
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StillTasty.com gives advice for both opened and unopened bottles of soy sauce.

Unopened is good for about three years when stored in a cool, dry place, such as your kitchen pantry.

Opened is good for about two years if it's kept refrigerated.

The "best by" dates are estimates, not guarantees. They indicate how long the product will be of the highest quality - not necessarily when it will expire or go off.
Source(s):
http://www.stilltasty.com/searchitems/search/soy%20sauce

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