A$1$ Auto Shop follows the revenue recognition principle. A$1$ services a car on August $31.$ The customer picks up the vehicle on September $1$ and mails the payment to A$1$ on September $5.$ A$1$ receives the check in the mail on September $6.$ When should $A1$ show that the revenue was recognized?

September $6$

August $1$

September $5$

August $31$