There is additional verbiage in the service let rules section that are required to fully spec out the implementation of the rules. First, it is made clear that if the server delivers the ball when the receiver is not ready, then the serve is counted as a service let.
The service is a let if:
The ball is served when the receiver is not ready.
USTA Friend at Court, ITF Rules of Tennis, Section 22.b
In “Not Quite Ready to Receive” it was discussed that if the receiver is not ready then the serve cannot be called a fault. I missed the subtlety of the usage of the word fault in that coverage of the rule. It was clear that the serve cannot be counted against the receiver if the receiver is not ready. The nuance is that the serve cannot be counted against the server if it does not fall in.
The remaining verbiage in the service let section pertains to when consecutive service lets are delivered.
In the case of a service let, that particular service shall not count, and the server shall serve again, but a service let does not cancel a previous fault.
USTA Friend at Court, ITF Rules of Tennis, Section 22
This dispenses with the service let rules with the exception of the ominous line I have come to dread… “Additional approved alternative procedures can be found in Appendix V.”
- United States Tennis Association (2020) Friend at Court. White Plains, NY