Incorrect spelling

ammended

Incorrect spelling, explanation: we do not double the consonant m in amend, so we do not double it also in its past form amended. The word was spelled back in Middle English as amenden, so with one m as well, and this spelling hasn’t been changed much since then. Therefore ammended is incorrect, and the correct form is amended.


Correct spelling

amended

Correct spelling, explanation: amended is the correct form as it is a past form from verb amend, also spelled with one m. Amend has its origins in Middle English amenden, so this spelling (one m) was also present back then. Therefore amended is correct and ammended is an incorrect form.

Definition of amended:
verb, past simple and past participle form of amend, to change, usually for the better; to add some modification
The income tax law has been amended recently.
If the price list is amended we will notify you.