Should, must and have to: advice and rules

Short answer: Use should for advice and must or have to for rules and needs. After should and must, use the plain verb with no to and no -s. Shouldn’t means it is not a good idea. Mustn’t means it is not allowed. Don’t have to means it is not necessary. For he, she and it, say has to, not musts.

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At a glance

In short

• should: advice. must / have to: rules and needs.
• After should and must: the plain action word.
• don't have to = not needed. mustn't = not allowed.

What is the rule for “Advice and rules: should, must, have to”?

The rule

should: advice. must / have to: a rule or a need. After should and must, the plain action word.

How it looks

should / shouldn't · must / mustn't · have to / has to · don't have to + plain action word

What it means

should: it is a good idea. must: it is necessary. don't have to: it is your choice. mustn't: it is not allowed.

When to use it

Use them to give advice and say rules.

How it works

• Is it advice (a good idea)? Use should.
• Is it a strong rule or a need? Use must or have to.
• After should and must, use the plain verb: should go, must go.
• Mustn’t and don’t have to are different: not allowed versus not needed.

Examples of “Advice and rules: should, must, have to”

• You should rest when you are tired.
  Advice.
• We must listen to the teacher.
  A rule.
• She shouldn't run near the pool.
  Advice: it is not a good idea.
• They don't have to clean the room.
  Not needed.
• You should drink more water.
  Advice.
• Students must wear a uniform.
  A school rule.
• I have to get up at six.
  A need from outside.
• You don’t have to come early.
  It is not necessary.

Common mistakes with “Advice and rules: should, must, have to”

• You must to wear a helmet. → You must wear a helmet.
  No to after must.
• He musts go. → He must go.
  must never takes -s.
• You mustn't come early. (it is not needed) → You don't have to come early.
  mustn't means not allowed.
• You should to see a doctor. → You should see a doctor.
  No to after should.
• She don’t have to wear a uniform. → She doesn’t have to wear a uniform.
  She takes doesn’t.

Exceptions: watch out

• has to
  have to changes with he / she / it: He has to bring his book.

Must or have to?

Must and have to are close. Must often shows the speaker’s own feeling. Have to often shows a rule from outside.

See also: Future: will and won't

Check yourself

1. Choose: “You ___ (should / must) wear a seat belt.” (law)
   Show the answer

   must A rule.

2. Choose: “Tomorrow is a holiday. You ___ come to school.” (don’t have to / mustn’t)
   Show the answer

   don’t have to It is not necessary.

3. Fix: “He musts go.”
   Show the answer

   He must go. Must never takes -s.

How to practice “Advice and rules: should, must, have to”

The interactive version adds step-by-step help, spoken instructions and a quick check. One rule card, one sound lesson and the first lesson of every stone are free to try; the rest is part of Full Access. See Full Access.

• Practice lesson: Advice and rules: should, must, have to

Questions

What is the past of “must”?

Use had to: I had to leave early. Must has no past form.

Is “should” a rule?

No. It is advice. If you want a rule, use must or have to.

What is the question form?

Should I go? Must I go? Do I have to go? Do you have to go?

More Texts and Talk rules

• Have you ever …? Experience: have / has + the past form tells about something you did (or never did) in your life, up to now.
• already, yet, just: already, yet and just go with have / has and tell about things that happened a short time ago.
• Present perfect or past simple?: A finished time (yesterday, last week) needs the past simple. Experience up to now needs have + the past form.
• unless: unless means if not. It says what could stop something.
• as … as, and comparing actions: as … as says two things are the same. not as … as says one is less. For actions use faster or more carefully.
• Linking sentences: also, however, for example, in the end: also, however, for example and in the end connect sentences. They start a new sentence, so put a full stop before them.

Part of the 📘 Grammar tool. Level G6: Texts and Talk. Đọc bằng tiếng Việt.

Written for English learners by the English for Fun team. How we write our lessons · Last updated 2026-11-05.

Reviewed by Chinh Q. Hoang, PhD, founder, English for Fun · 2026-10-30

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