Learn Hardcore Dutch: Wie te laat incheckt, die betaalt een toeslag.

Here wie is a free relative pronoun meaning whoever / anyone who. It does not ask a question; it introduces a subordinate clause referring to people in general. It’s only used for persons (for things/abstracts, Dutch uses wat).

Why is the verb at the end in wie te laat incheckt? Shouldn’t it be checkt … in?

Because wie introduces a subordinate clause, the finite verb goes to the end. With separable verbs like inchecken, the particle stays attached in subordinate position:

Main clause: Hij checkt (te laat) in.
Subordinate: … dat hij (te laat) incheckt. So: Wie te laat incheckt …

What is the role of die after the comma?

It’s a demonstrative pronoun in the correlative pattern wie … die … (“whoever … that person …”). It picks up the generic subject from the first clause and serves as the explicit subject of the main clause: “Whoever checks in too late, that person pays a surcharge.”

Can I leave die out?

Yes. Both are correct:

Wie te laat incheckt, betaalt een toeslag. (very common)
Wie te laat incheckt, die betaalt een toeslag. (a bit more emphatic/formal)

Why is it betaalt (singular) and not betalen (plural)?

Grammatically, wie is singular, so the verb agrees: die betaalt. If you want an explicitly plural subject, use:

Zij die te laat inchecken, betalen een toeslag. or
Degenen die te laat inchecken, betalen een toeslag.

Is there a more conversational way to say this?

Yes:

Als je te laat incheckt, betaal je een toeslag.
Check je te laat in, dan betaal je een toeslag. These are common in everyday speech; wie … die … sounds more like rules/regulations.

Why is it te laat and not just laat?

te laat = “too late / tardy,” i.e., after a required deadline or time.
laat alone is more about a late hour or lateness in a neutral sense (e.g., Ik werk laat = I work late), but for being tardy to something, Dutch typically says te laat komen/inchecken.

How does the separable verb inchecken conjugate here?

Infinitive: inchecken
Present (main clause): ik check in, hij checkt in
Present (subordinate): … dat ik incheck, … dat hij incheckt
Perfect: ik heb ingecheckt
With a modal: ik moet inchecken (no separation after a modal)

Is the comma before die required?

When a subordinate clause comes first, Dutch normally places a comma before the main clause. So a comma is standard (and with die it’s clearly needed).

What’s the nuance of toeslag? Is it a fine?

toeslag = surcharge/supplement/extra fee (often predetermined and legitimate)
boete = fine/penalty (for breaking a rule) In travel contexts, toeslag is common for extra costs; a boete implies a penalty.

What gender and plural does toeslag have?

It’s a de-word: de toeslag; plural: de toeslagen.

Can I replace die with hij or zij?

Not idiomatically in this generic rule-like statement. die is the natural choice for the correlative wie … die …. For a casual generic, switch to second person: Als je …, (dan) betaal je …

Could I start the sentence with Die te laat incheckt, …?

Generally avoid that unless there is an explicit antecedent for die. The standard generic pattern is Wie … die … (or Degenen die … / Zij die … for plural).

What’s the counterpart for things: is it wat … dat …?

Yes. For non-persons/abstracts, Dutch uses the correlative wat … dat …:

Wat kapot is, dat gooien we weg. (“Whatever is broken, we throw away.”)

Why is it een toeslag and not de toeslag?

Because the fee is not a specific, previously identified surcharge; it’s any applicable surcharge. If a specific surcharge had already been introduced, de toeslag could be used.

How would I say “must pay” instead of just “pays”?

Wie te laat incheckt, moet een toeslag betalen. Note the main-clause V2 order with moet and the infinitive betalen at the end.

Any pronunciation tips for tricky parts?

wie: initial Dutch w is like a soft English v/w; ie as long “ee” in “see.”
checkt: the ch here is like English “ch” in “check,” and the final -t is pronounced.
toeslag: oe sounds like “oo” in “food”; final g/ch is the Dutch guttural sound.

Is there a good synonym for inchecken?

aanmelden can work in some contexts (“to register/check in”), but for travel/hotels/airlines inchecken is the standard term.