Incorrect spelling


Incorrect spelling, explanation: speaking of the monetary meaning of the word pay and repay, this verb is irregular, therefore the correct form is repaid. Repayed in this context is incorrect. Repaid is an irregular past form of the verb repay. However, please keep in mind, that there is such a word as repayed, which is a past form of repay in nautical meaning (as to seal to prevent leaks).

Correct spelling


Correct spelling, explanation: repaid is a past simple and past participle form of the verb repay. Because this is unusual (due to the fact, that we change y to i only if y is preceded by a consonant), the verb pay, thus also repay is considered irregular. Therefore repayed is incorrect and repaid is the correct form.
Note: there is such word as repayed in nautical terms (past form of repay, meaning to close the leak).

Definition of repaid:
verb, past simple and past participle form of repay, to pay back
Our debt needs to be repaid quickly.
Project loans must be repaid by the end of December.