Is there any limit on the amount of Epic Rewards balance I can have on my account?

The maximum Epic Rewards balance an Epic Games Store user may have at any given time is USD$500 (or its equivalent in the Participant’s local currency), or the maximum allowable in the user’s local jurisdiction, if that amount is less than the equivalent of $500USD. If a user’s Epic Rewards balance will exceed $500 after an eligible purchase, the user will not receive the portion of the Epic Rewards for the purchase which, when added to the user’s existing Epic Rewards balance, would exceed $500USD. For example, if a user has an Epic Rewards balance of $495USD and the user makes a $100 purchase that is eligible for $10 in Epic Rewards, the user will receive $5USD in Epic Rewards. You can check your Epic Rewards balance at any time in your Account. 

For more information, see: Epic Games Store EULA (Opens in a new tab)