Answer:
Dr Trade Receivables $400
Cr Service Revenue $400
Explanation:
According to accrual accounting system, once the share of consideration from the part of company is delivered the company must recognize sales. As the company has not been billed for its services, which means the customer has not yet paid so the receivable account would be debited and the company must also recognize revenue because it has delivered its share.
Increase in revenue must be credited and increase in receivables must be debited.
Dr Trade Receivables $400
Cr Service Revenue $400