Google sends a personal identification number (PIN) by physical mail to all AdSense account holders upon becoming eligible to receive payments. Eligibility is based on achieving a threshold earnings level, set at $10.00 for U.S. AdSense accounts. Thresholds and currencies for other countries are listed on the Google AdSense Payment Threshold information page.
AdSense accounts cannot take receipt of their earnings without this PIN.
This is a scaled image of the PIN mailer used by AdSense. The postcard-type mailer is sent via standard post to the account holder’s address of record with Google.
The dimensions are given as 6.0 inches wide and 4.5 inches in height when mailed. When opened, the total height doubles to 9.0 inches. Additional details can be found on the Google AdSense PIN Process Help page.