Is expiation (kaffarah) required for a pharmacist who adds items to customers' invoices that were not purchased, at their request, given the sinfulness of such an act?

Adding items not listed in the invoice is impermissible because it constitutes deception, falsehood, and betrayal. Its expiation is repentance, remorse, seeking forgiveness, and increasing good deeds, as Allah the Almighty says: "Indeed, good deeds do away with evil deeds," and the Prophet (peace be upon him) said: "And follow up a bad deed with a good deed which will wipe it out." If the pharmacist consumed ill-gotten wealth due to this, he must return it to its owner if known; otherwise, he should donate it to charitable causes.