Original: Any shortfall in payments could then result in garage arrears and may lead to a Notice to Quit being issued for the garage.
Simplified: Any payments paid for less than the agreed amount could then result in garage arrears and may lead to a Notice to Quit being issued for the garage.
Simplified: Any shortfall in payments could then result in you owing money, and may lead to a Notice to Quit being issued for the garage.
Simplified: Any mistakes in payments could then result in garage arrears and may lead to a Notice to Quit being given to the garage.