Your MarTrust Card's billing address is the address your employer registered when your MarTrust Account was first set up. This is the address held on file with MarTrust — it isn't something you set separately for the card itself.
You'll usually need to provide this when a merchant asks you to confirm a billing address to complete a transaction. Many merchants check the address on the card to verify the payment before it goes through, so having the correct one on hand can help prevent a decline.
If you're not sure which address is currently on file or if it needs updating, please contact support and we can help you confirm or correct it.