Once a box of baking soda is opened, it has a shelf life of about six months to a year. If you happen to find an unopened box, chances are it may still be good even if it's past the expiration date (generally about 18 months from the time it went on sale).

What happens if you use expired baking soda?

Should I throw away old baking soda? Baking Soda does not “go bad.” It just loses its efficacy! So, there are other uses for baking soda, even when the potency has diminished.

Will expired baking soda hurt you?

Baking soda, like baking powder, can lose potency over time (using the expired stuff won't hurt you—it just won't be effective in your recipes).