Ne jette pas le ticket de caisse, il peut servir de preuve.

Because jette is in the imperative, the form used for commands. In French commands, the subject pronoun is usually omitted.

So instead of Tu ne jettes pas..., French says:

Ne jette pas... = Don’t throw away...

This is normal for imperative forms:

• Mange ! = Eat!
• Ne parle pas ! = Don’t speak!

In this sentence, jette is the tu imperative form of jeter.

In a negative imperative, ne goes before the verb and pas goes after it:

Ne jette pas ...

This is the standard pattern for negative commands:

• Ne bouge pas. = Don’t move.
• N’oublie pas. = Don’t forget.
• Ne pars pas. = Don’t leave.

So Ne jette pas le ticket de caisse literally follows the same structure as Don’t throw away the receipt.

This is a spelling change in the verb jeter.

In some forms, the t is doubled before a silent ending:

• je jette
• tu jettes
• il jette

The imperative tu form matches the present tense tu form without the subject pronoun, so:

• tu jettes → jette !
• ne jette pas !

This is just how this verb is conjugated. A similar pattern happens with some other verbs, especially verbs like appeler.

Using le here refers to a specific receipt — the one you already have or are talking about.

• Ne jette pas le ticket de caisse = Don’t throw away the receipt.
• Ne jette pas un ticket de caisse would sound more like don’t throw away a receipt, which is less natural in this context.

French often uses the definite article when referring to a specific thing already known in the situation.

Ticket de caisse is the usual French term for a store receipt or cash-register receipt.

Literally:

• ticket = slip / ticket
• de caisse = from the cash register / checkout

So it is the receipt you get after paying in a shop.

A learner may expect something like reçu, but in everyday French, ticket de caisse is very common for shopping receipts.

Servir de means to serve as.

So:

• servir de preuve = to serve as proof
• servir de modèle = to serve as a model
• servir d’exemple = to serve as an example

In your sentence:

il peut servir de preuve = it can serve as proof

This is a very common French structure: servir de + noun.

After servir de, French often uses a noun without an article when it describes the role or function of something.

So:

• servir de preuve = serve as proof
• servir de référence = serve as a reference
• servir de base = serve as a basis

This is similar to English, where we often say serve as proof, not necessarily serve as a proof.

If you said servir d’une preuve, it would sound less natural here because the idea is not one proof among others, but the role of the receipt as proof.

Il refers to le ticket de caisse.

French often uses a pronoun to avoid repeating the noun:

• le ticket de caisse → il

So the sentence means: Don’t throw away the receipt; it can serve as proof.

Even though ticket is not a person, French still uses il because ticket is a masculine noun.

Yes, in informal spoken French, you might hear:

Ne jette pas le ticket de caisse, ça peut servir de preuve.

That is very natural in conversation.

The difference is:

• il is a bit more grammatically tied to le ticket
• ça is more informal and conversational

In careful written French, il is a very good choice.

Because the sentence links two closely related ideas:

1. Ne jette pas le ticket de caisse
2. il peut servir de preuve

French, like English, can join closely connected clauses with a comma, especially when the second explains the first.

You could also say:

• Ne jette pas le ticket de caisse, car il peut servir de preuve.
• Ne jette pas le ticket de caisse : il peut servir de preuve.

All of these are possible. The comma version is concise and natural.

In standard written French, yes:

Ne jette pas le ticket de caisse...

In informal spoken French, people often drop ne:

• Jette pas le ticket de caisse...

But learners should know that:

• keeping ne is the correct standard form
• dropping ne is very common in everyday speech

So if you are writing or speaking carefully, use ne ... pas.

This is a very common learner question. In affirmative imperatives, many -er verbs drop the final s in the tu form:

• Tu jettes → Jette !
• Tu parles → Parle !

So the affirmative command is:

• Jette le ticket.

In the negative imperative, it stays the same:

• Ne jette pas le ticket.

So the lack of s is normal for -er verbs in the tu imperative.

One detail: in certain cases, an s reappears before y or en for pronunciation:

• Vas-y
• Manges-en

But that does not apply here.

It is informal or neutral, because the command is in the tu form:

Ne jette pas...

If you wanted to be more formal or address more than one person, you would use the vous imperative:

Ne jetez pas le ticket de caisse, il peut servir de preuve.

So:

• ne jette pas = singular informal
• ne jetez pas = formal singular or plural

The rest of the sentence stays the same.