I have two miso's :
the on on the R is from Tj's , and I refrigerate after opening.
the packet says it expires 6 / 25 .
the left came from MarketBasket . I have not opened it yet.
it does not say anything on the packet about expiring at all .
it does have these number on the back : 5512 044.
miso has so much salt in it , as the idea was to preserve via salting
it might not expire as such for some time.
might not kill you , in the distant future
but might taste less interesting.