I know what to sent (send)

Short answer: when "to" marks an infinitive, follow it with the base verb (to send), not the past tense or past participle (sent).

Below: the rule, clear examples you can copy, context-specific rewrites (work, school, casual), and quick checks to fix sentences fast.

Quick answer

Use the base form after to when it begins an infinitive phrase: say what to send, where to go, how to choose - not what to sent, where to went, how to choosed.

Infinitive structure: to + base verb (to send, to go, to choose).
Don't use past tense or past participle after the infinitive marker (not to sent, went, chose).
If to is a preposition, follow it with a noun or an -ing form instead (look forward to meeting).

Core grammar: when to is the infinitive marker

When "to" introduces an action (an infinitive), it needs the base verb: to send, to read, to write. A past form like sent is incorrect after that "to."

When "to" is a preposition, it pairs with a noun or an -ing form: to the store, to meeting you.

Infinitive: I need to send the file.
Preposition: I look forward to meeting you.

Wrong: I don't know what to sent to her.
Right: I don't know what to send to her.
Wrong: She asked where to went for lunch.
Right: She asked where to go for lunch.

Hyphenation, spacing, and surface traps

Never hyphenate "to" and the verb: write "to send," not "to-send." Keep a single space and the same verb form even if punctuation interrupts the clause.

No hyphen: what to send, where to go.
Single space: to send. Punctuation doesn't change the rule.
Check after commas and dashes; the infinitive still needs the base verb.

Usage: What to send? (correct)
Wrong: What-to-send? (do not hyphenate the infinitive)

Common wrong/right pairs you can copy

Swap in the base verb in these patterns and your sentence will be correct.

Wrong: I don't know what to sent.
Right: I don't know what to send.
Wrong: Tell me what to brought to the potluck.
Right: Tell me what to bring to the potluck.
Wrong: I can't decide what to wore.
Right: I can't decide what to wear.
Wrong: She didn't know how to cooked the dish.
Right: She didn't know how to cook the dish.
Wrong: We need to decide what to chose for the cover photo.
Right: We need to decide what to choose for the cover photo.
Wrong: He asked what to did next.
Right: He asked what to do next.

Work examples: emails, instructions, and subject lines

Use these as direct replacements in emails, reports, and internal docs. Small wording tweaks can tighten tone while correcting the verb.

Wrong: Please let me know what to sent to the client.
Right: Please let me know what to send to the client.
Wrong: I'm not sure what to attached to the proposal.
Right: I'm not sure what to attach to the proposal.
Wrong: Tell me what to scheduled for the kickoff.
Right: Tell me what to schedule for the kickoff.
Rewrite:
Original: Please let me know what to send to the client. Better: Let me know which files I should send to the client.

School examples: assignments, emails to professors, and study notes

Professors and graders expect correct verb forms. These swaps are safe for assignments and polite emails.

Wrong: I don't know what to handed in for the group project.
Right: I don't know what to hand in for the group project.
Wrong: Can you tell me what to readed before class?
Right: Can you tell me what to read before class?
Wrong: I'm unsure what to wrote for the introduction.
Right: I'm unsure what to write for the introduction.
Rewrite:
Original: I don't know what to hand in for the group project. Better for email: Could you confirm which documents we should hand in for the group project?

Try your own sentence

Test the whole sentence rather than the isolated phrase; context usually makes the right choice clear.

Casual examples: texts, social posts, and conversations

Casual messages still sound better with the correct verb. Most fixes are short swaps.

Wrong: I don't know what to posted tonight.
Right: I don't know what to post tonight.
Wrong: Any idea what to brought to the BBQ?
Right: Any idea what to bring to the BBQ?
Wrong: Not sure what to chooseed for my outfit.
Right: Not sure what to choose for my outfit.
Rewrite:
Original: Any idea what to bring to the BBQ? Quick
rewrite: What should I bring to the BBQ?

Rewrite help: fast edits you can use now

Checklist:

1) Is "to" followed by a verb naming an action? If yes, use the base form.
2) Replace past forms with base forms (sent → send, brought → bring).
3) Read the sentence aloud; if it sounds natural, it's probably correct.

Rewrite:
Original: I don't know what to sent to the client. Quick fix: I don't know what to send to the client.
Rewrite:
Original: She can't decide what to wore for the interview. Quick fix: She can't decide what to wear for the interview.
Rewrite:
Original: We're not sure what to bought for the event. Quick fix: We're not sure what to buy for the event.
Rewrite:
Original: Should I sent the PDF now? Better: Should I send the PDF now?
Rewrite:
Original: Tell me what to brought. Better: Tell me what to bring.

Memory tricks and quick checks

Use the "I will" test: insert "I will" before the verb. If "I will + verb" sounds right, use the base form after to. If "I will + past" sounds wrong, avoid the past form after to.

Mnemonic: To = Action. If it names an action, use the base verb.
Quick test: I will send → to send (correct). I will sent → wrong.
If "to" is followed by a noun or -ing, treat it as a preposition instead.

Check: I don't know what to (I will) send. If "I will sent" feels wrong, change sent to send.
Check: I'm looking forward to (I will) meeting you. "I will meeting" is wrong, so use meeting here.

Similar mistakes to watch for

Once you stop using past forms after infinitives, many related errors disappear. Watch these common patterns.

Past tense after infinitive: wrong → He didn't know what to did; right → He didn't know what to do.
-ing after infinitive: wrong → I want to going; right → I want to go.
Base form after preposition: wrong → I'm looking forward to meet you; right → I'm looking forward to meeting you.

Wrong: He didn't know what to did.
Right: He didn't know what to do.
Wrong: I want to going to the store.
Right: I want to go to the store.
Wrong: I'm looking forward to meet you.
Right: I'm looking forward to meeting you.

FAQ

Is "to sent" ever correct?

Not as to + verb. When "to" is the infinitive marker, use the base verb (to send). "Sent" can appear elsewhere (in a separate clause or passive construction) but not as to + sent.

How can I tell if "to" is an infinitive marker or a preposition?

If a base verb that names an action directly follows "to," it's an infinitive marker (to send). If a noun or an -ing form follows, "to" is a preposition (to the store, to meeting).

What quick edit catches most errors before I send an email?

Insert "I will" before the verb: if "I will + verb" sounds right, use the base form after to. If "I will + past" sounds wrong, change the verb to the base form.

Are grammar checkers reliable for this mistake?

Most grammar checkers flag patterns like "what to sent" and suggest the base form. Always read the suggestion to confirm it matches your meaning.

Why do native speakers still make this error?

People mix up forms when writing quickly; past forms are familiar and sometimes transfer from other languages. Practicing the "I will" test helps break the habit.

Quick next step

Before you send an important message, scan for "to" followed by a verb and use the "I will" check. If you want extra certainty, run the sentence through a grammar tool for a final pass.