Learn Hardcore Spanish (Spain): Mañana no pagaré la cuenta yo, sino que la pagarás tú. - Tomorrow I will not pay the bill; rather, you will pay it.

Spanish usually drops subject pronouns, but it adds them for emphasis or contrast. Here, the speaker contrasts the subjects: not me, but you. Placing the subject pronoun at the end (la pagarás tú) strongly focuses the contrast on tú.

Why is it sino que and not pero?

Use sino (que) to correct or replace a previous negative idea (not X, but rather Y). Use pero to add a contrasting idea without canceling the first one.

Correction: No la pagaré yo, sino que la pagarás tú.
Contrast/addition: No la pagaré yo, pero puedo dejar propina.

What’s the difference between sino and sino que?

sino is used when the second element is a word or phrase (no verb): No café, sino té.
sino que is required when the second element is a clause with a conjugated verb: No la pagaré yo, sino que la pagarás tú.
In this sentence, the second part has the verb pagarás, so you need sino que.

Can I say tú la pagarás instead of la pagarás tú?

Yes. Both are correct:

Tú la pagarás: fronted subject; still emphatic.
La pagarás tú: subject at the end; often sounds even more contrastive/focused in this context.
Both communicate “YOU will pay it (not me).”

What does the clitic la stand for here, and why not le?

La is the direct-object pronoun referring to the feminine noun la cuenta. It agrees in gender and number. Le is used for indirect objects (and for some animate masculine direct objects in leísmo areas), but not for a thing like a bill.

Where do object pronouns go with verbs like pagar?

Before a conjugated verb: No la pagaré (yo).
Attached to an infinitive: No voy a pagarla (yo).
Attached to a gerund: Estoy pagándola.
Attached to an affirmative command: Págala tú.
In the target sentence, la goes before the finite verb: la pagarás.

Can I drop la in the second clause and say sino que pagarás tú?

You can, and it will be understood (“but rather you will pay”), but Spanish tends to keep the direct-object pronoun or restate the noun to avoid ambiguity: sino que la pagarás tú or sino que pagarás tú la cuenta are clearer and more idiomatic.

Does mañana have to be at the beginning, and do I need a comma?

No. Mañana can go first or later:

Mañana no la pagaré yo… (common; comma after a short introductory adverb is optional)
No la pagaré yo mañana…
Position mainly affects rhythm and emphasis, not correctness.

Why use the simple future (pagaré/pagarás) instead of ir a + infinitive or the present?

All three can express future plans:

Simple future: pagaré/pagarás (neutral, sometimes a bit more formal or decisive; can also express conjecture in other contexts).
Periphrastic future: voy a pagar/vas a pagar (very common, colloquial).
Present with a future time: mañana pagas tú (very natural for scheduled/near-future actions).
Here, any option would work in Spain.

Why do pagaré and pagarás have accents, and why does tú have one?

pagaré/pagarás take written accents to keep the stress on the final syllable (future tense endings). Without accents (pagaras), the form is a different tense/mood (past subjunctive or second-person informal command in voseo).
tú (you) takes an accent to distinguish it from tu (your).
Also note ñ in mañana is a distinct letter, not an accented n.

Could I say No la pagaré yo, sino tú?

Yes. When the second element is just a noun/pronoun (no verb), sino (without que) is correct: No la pagaré yo, sino tú. The original uses a full clause in the second part, hence sino que.

What are very natural ways in Spain to say the same idea?

Common alternatives:

Mañana pagas tú.
Mañana te toca a ti. (It’s your turn tomorrow.)
Mañana invitas tú. (Spain: “you’re treating/picking up the bill.”)

Could I use pero with sí to get a similar meaning?

Yes: No la pagaré yo, pero tú sí (la pagarás).
This is acceptable and natural. The nuance is slightly different: sino (que) corrects the first clause; pero presents a contrast without the same corrective force.

How would this change for plural “you” in Spain?

Use vosotros with the future ending -éis:

… sino que la pagaréis vosotros.
In most of Latin America, you’d use ustedes with -án: … sino que la pagarán ustedes.

What’s the difference between sino and si no?

sino = but rather/except: No él, sino ella.
si no = if not: Si no vienes, me voy.
They’re not interchangeable.

Why not the subjunctive (pagues) after sino que?

Here we have two coordinated indicative clauses stating facts/plans: no pagaré… sino que pagarás…
Subjunctive would appear if the main verb required it (wish, doubt, etc.): No quiero pagarla yo, sino que la pagues tú. Different structure, different meaning.

Is la cuenta the normal way to say “the bill” in Spain?

Yes, for a restaurant bill use la cuenta. La factura is more like an invoice or formal bill (e.g., utilities, business), though you may hear it in some service contexts.