Amoxicillin capsules and tablets have an expiry of around 2 years and, provided they are stored as recommended and in the original packaging, there will be a small lee way of safety if used beyond expiry. Amoxicillin suspension is different and has a very short shelf life of about 7-10 days once it is prepared.

The expiry date is the last day that the pharmaceutical manufacturer guarantees the safety of the medication and it is mandatory on every medicine. The expiry date is estimated by stability testing.

Amoxicillin is an antibiotic used to kill susceptible micro-organisms responsible for bacterial infections. Amoxicillin is available as capsules, tablets and a suspension.

On a slightly different note antibiotics should be used only for whatever they were prescribed for and to whom.

Also, with most antibiotic courses they are prescribed to be taken "until finished".

See also:
https://www.drugs.com/article/drug-expiration-dates.html
https://www.drugs.com/amoxicillin.html