Learn Portuguese (Portugal): Não fazemos nada se a documentação não estiver pronta. - We do not do anything if the documentation is not ready.

The word se (if) introduces a condition that might happen in the future. In Portuguese, when an 'if' clause talks about a future possibility, we must use the Future Subjunctive tense.

Where does the irregular form estiver come from?

For irregular verbs, you build the Future Subjunctive from the 'they' form of the simple past tense. The past tense is estiveram (they were). You drop the '-am' to get the base estiver-, and since the subject a documentação is a singular 'it', you don't add any extra ending.

Why are both Não and nada used in the first clause?

In Portuguese, double negatives are required in this structure. When a negative word like nada (nothing or anything) comes after the verb, you must put não before the verb.

Why use a form of estar for 'to be' instead of ser?

We use estar because being ready (pronta) is a temporary state or condition of the documentation, rather than a permanent characteristic.