Learn Dutch: Je mag de goederen uitladen zodra de planner klaar is. - You may unload the goods as soon as the planner is ready.

Zodra (as soon as) is a subordinating conjunction. This means it introduces a dependent clause and forces the conjugated verb (in this case, is) to the very end of that clause.

Why is uitladen at the end of the first clause, rather than next to mag?

The first part of the sentence uses the modal verb mag (may). In Dutch, when you use a modal verb, the main action verb (uitladen) is pushed to the end of its clause, wrapping around the object de goederen.

I know uitladen is a separable verb. Why isn't it split up here?

Separable verbs only split when they are the conjugated, active verb in a main clause (for example: ik laad de goederen uit). Because the helper verb mag is doing the grammatical work here, uitladen stays in its full, combined infinitive form at the end of the clause.

Can I use goederen in the singular if I only have one item to unload?

Not really. When referring to freight, merchandise, or cargo, goederen is basically always plural, exactly like the English word 'goods'.