Lets and Service Faults in Tennis: When a Serve Is Replayed or Lost

Two things can go wrong with a serve, and they have very different consequences. A fault costs the server one of their two attempts. A let costs nothing and the serve is taken again.

What counts as a fault

A serve is a fault if the ball lands outside the correct service box, if it hits the net and fails to land in that box, or if the server misses the ball entirely having attempted to strike it. Two faults in succession is a double fault and the point goes to the receiver.

Tossing the ball and catching it without swinging is not a fault, because no attempt to strike was made. Swinging and missing is.

Foot faults

A foot fault occurs when the server's foot touches the baseline or the court inside it before the ball is struck, or when the server moves outside the permitted area behind the baseline between the centre mark and the sideline extension. It is judged at the moment of contact, not afterwards, and it carries the same penalty as any other fault.

Foot faults are called far less often in recreational play than they occur, which is one reason players are often surprised by them in officiated matches. The rule is about where the feet are when the ball is struck, not about stepping in during the follow-through.

What counts as a let

The service let is the common one: the ball clips the net cord and still lands in the correct service box. The serve does not count, neither as a fault nor as a good serve, and it is taken again. A first serve that clips the net and goes in is replayed as a first serve, so the server keeps both attempts.

A let is also called when the serve is delivered before the receiver is ready, or when play is interrupted by an outside disturbance such as a ball rolling onto court. In those cases the whole point is replayed, not just the serve.

Let rule variations

Some competitions play no-let, where a serve that clips the net and lands in remains live. It is used in a good deal of college and league tennis, chiefly to speed matches up and remove a source of dispute on unofficiated courts. As with no-advantage scoring, it is an approved alternative rather than the default; the standard rule and the permitted variations are set out in the ITF Rules of Tennis, and each event states which it uses.

Calling your own lines

Most tennis is played without officials, which means the players call the lines on their own side of the net. The convention is that a ball is good unless you are certain it was out, and that a call must be made immediately. A player cannot play a ball, lose the point and then call it out.

The same applies to lets. On an unofficiated court the receiver is generally best placed to hear a service let, but either player may call it, and again it must be called at once rather than after the point has developed. Disputes about lets are one of the main reasons some competitions adopt the no-let rule.

The second serve

Because a fault costs an attempt rather than the point, the two-serve structure produces one of the sharpest risk trade-offs in the sport. A first serve can be struck at full pace precisely because missing it is survivable. A second serve cannot, since missing it loses the point outright.

The practical consequence is that second-serve quality, not first-serve speed, tends to separate players. A weak second serve is attacked, and a player who doubts theirs will over-press the first to avoid needing it — which produces more first-serve faults and more second serves. The pattern compounds, and it is why coaches treat the second serve as the more important of the two to build.