Fine mood contrasts: el hecho de que, que yo sepa, digan lo que digan

By now you know the big rules: the subjunctive for wishes, emotions, doubt and the unknown (The subjunctive for wishes and requests: quiero que, ojalá, Doubt and denial: no creo que vs creo que, Subjunctive in relative clauses: busco a alguien que sepa). At C1 the interesting cases are the ones where both moods are grammatical and the choice says something about how the speaker presents the information: as news (indicative) or as something known, evaluated or not yet defined (subjunctive).

El hecho de que

El hecho de que ("the fact that") looks as if it should take the indicative: it introduces a fact. In practice, when the clause is the topic of the sentence (usually at the start, as the subject) and the main verb evaluates it, the subjunctive is the norm. The fact is treated as already known; what matters is the speaker's judgement of it.

• El hecho de que no haya contestado me preocupa.The fact that he hasn't replied worries me.

The indicative appears mainly when the clause comes after the verb and presents new information, often after prepositions: Esto se explica por el hecho de que los precios subieron. The RAE's Nueva gramática describes both; for an opening el hecho de que in careful writing, choose the subjunctive.

Restrictive formulas: que yo sepa

A small set of fixed phrases limit what you are claiming. They always take the subjunctive:

• que yo sepa = as far as I know
• que yo recuerde = as far as I remember
• que yo vea = as far as I can see (less common)

• Que yo sepa, el contrato no se ha firmado todavía.As far as I know, the contract hasn't been signed yet.
• Que yo recuerde, nunca hemos tenido un problema así.As far as I can remember, we've never had a problem like this.

Reduplicated concessives: digan lo que digan

Spanish says "whatever / wherever / however" by repeating a subjunctive verb around a relative word. The meaning is "it makes no difference":

• Digan lo que digan, el proyecto sigue adelante.Whatever they say, the project is going ahead.
• Cueste lo que cueste, vamos a terminar la obra este año.Whatever it costs, we're going to finish the building work this year.
• Quieras o no, mañana hay que madrugar.Like it or not, we have to get up early tomorrow.

In a past narrative the formula moves to the imperfect subjunctive, and the same form is normally repeated (-ra … -ra or -se … -se):

• Fuera donde fuera, siempre se encontraba con algún conocido.Wherever she went, she always ran into someone she knew.

Verbs that change meaning with the mood

Some verbs mean one thing with the indicative and another with the subjunctive:

• Siento que estés pasando por un momento tan difícil.I'm sorry you're going through such a hard time.
• Siento que algo ha cambiado entre nosotros.I feel that something has changed between us.
• Le dije que llegaba tarde.I told him I was running late.
• Le dije que llegara pronto.I told him to arrive early.
• Entiendo que estés harto, pero no podemos cambiar la fecha.I understand you being fed up, but we can't change the date.

No es que … es que

No es que rejects a possible explanation, so it takes the subjunctive; the real reason follows with es que + indicative.

• No es que no me guste tu idea, es que no tenemos presupuesto.It's not that I don't like your idea, it's that we don't have the budget.

Lo que + indicative or subjunctive

Lo que quieres is a specific thing you already want; lo que quieras is "whatever you want", still undefined.

• Haz lo que quieras, a mí me da igual.Do whatever you like, I don't mind.

Latin America

All of these contrasts work the same way everywhere. In the past forms both -ra and -se are correct, but -ra is far more frequent in Latin America (fuera donde fuera).

Common mistakes

• Que yo sé, no ha llamado nadie: the formula is fixed with the subjunctive, que yo sepa.
• Dicen lo que dicen, no cambio de opinión: the concessive needs the subjunctive on both sides, digan lo que digan.
• Using siento que + indicative to apologise: Siento que estás enfermo means "I sense you're ill", not "I'm sorry you're ill" (siento que estés enfermo).
• Le dije que venía a las nueve when you meant an instruction: to tell someone to do something, use the subjunctive, le dije que viniera.
• No es que no quiero: after no es que, use the subjunctive, no es que no quiera.