fill in
2 meanings
write the needed information on a form or document
What does "fill in" mean in this sense?
Examples
- Please fill in your name and contact details at the top of the page.
- I filled the application form in and sent it off yesterday.
- Have you filled in the survey yet? It only takes two minutes.
How to use it
The most common pattern — the form or document follows the particle directly.
Could you fill in this registration form before your appointment?
With short noun objects, the object can sit between 'fill' and 'in'. Both positions are natural.
She filled the application form in and posted it the same day.
When the object is a pronoun, it must go between 'fill' and 'in' — never after 'in'.
Here's the questionnaire — please fill it in and hand it back.
The passive is natural, especially in instructions where the focus is on the form rather than the person.
Both sections of the form must be filled in before you submit it.
Very common in everyday situations where someone explains what another person must do.
You'll need to fill in a short survey at the end of the course.
Common Collocations
Common Mistakes
'Fill up' is used for containers (like filling up a glass or a petrol tank), not for forms. Always use 'fill in' (or 'fill out') when you mean completing a form.
When you replace the object with a pronoun like 'it' or 'them', the pronoun must go between 'fill' and 'in', not after 'in'.
'Fill in' in this sense only takes a form or document as its object. If the object is a person, you are using a completely different sense of the phrasal verb — as in 'fill me in on what happened', which means to update someone with information.
Usage
'Fill in' is the standard British English choice; Americans tend to say 'fill out', but both are understood worldwide. Use 'fill it in' (not 'fill in it') when replacing the object with a pronoun.
tell someone about something they missed or need to know
Sense 2: What does "fill sb in" mean?
Examples
- I missed the last meeting — can you fill me in on what was decided?
- She quickly filled the new manager in on the situation before the call.
- Don't worry, I'll fill you in when I get back from the conference.
How to use it
This is the most common pattern. The person comes between 'fill' and 'in', and 'on' introduces the topic.
Can you fill me in on what was decided at the meeting?
When the topic is clear from context, you can drop the 'on' part and just name the person.
I missed the first half — someone fill me in!
With a noun object (not a pronoun), separation is still common and natural.
Can you fill the new staff members in on the latest changes?
The passive form is possible, especially when you want to focus on the person who received the information.
I wasn't filled in on the new schedule before the project started.
Use this pattern to promise to give someone information at a future point.
I can't explain everything now, but I'll fill you in when I'm back.
Common Collocations
Common Mistakes
When you mention the topic, you must use 'on' before it. Leaving it out or using 'about' instead sounds unnatural.
Pronouns like me, him, her, us, and them must go between 'fill' and 'in'. Placing them after 'in' is grammatically wrong.
'Fill in' has another common meaning: to complete a form or document. In that sense, the object is always a document, not a person. Make sure the object after 'fill' is a person or group when you mean to inform someone.
Usage
This phrasal verb is neutral and works in both workplace and casual contexts. It is common in spoken English and informal emails, but avoid it in very formal written documents — use 'inform' or 'brief' instead.
Frequently Asked Questions
What is the difference between 'fill in' and 'fill out'?
They mean exactly the same thing when talking about completing a form. 'Fill in' is the more common choice in British English, while 'fill out' is preferred in American English. Both are understood everywhere, so you won't make a mistake using either one.
Does 'fill in' always mean completing a form?
No — 'fill in' has other meanings in English. For example, it can mean to substitute for someone ('Can you fill in for me today?') or to update someone with missing information ('Fill me in on what I missed'). On this page, we are only looking at the form-completion meaning, where the object is always a document, form, or questionnaire.
Can I use 'fill in' in official instructions, like on a website or printed form?
Yes, 'fill in' is very common in official instructions. You will often see phrases like 'Fill in all required fields' on websites or 'Fill in your details below' on printed forms. It works well in both formal instructions and casual conversation.
What kinds of things can I 'fill in'?
The object is always something written or digital that has blank spaces for information — for example, a form, an application, a questionnaire, a survey, a registration form, or individual fields, boxes, or blanks within a document. You wouldn't use 'fill in' with objects that aren't documents of this kind.
Does 'fill someone in' always need 'on'?
Only when you mention the topic. If the topic is already clear from the conversation, you can leave out 'on' and just say something like 'fill me in'. But if you name the topic, 'on' is required — for example, 'fill me in on the meeting'.
What kinds of topics can follow 'on'?
Almost anything a person might have missed or need to know: 'fill me in on the details', 'fill me in on the situation', 'fill me in on what happened', 'fill me in on the latest'. It works with events, plans, discussions, news, and background information.
Can I use 'fill in' in a work email?
Yes, it's perfectly fine in informal or semi-formal work emails and messages. For example: 'Could you fill me in on the key points from Friday's call?' If the email is very formal — such as an official report — you might prefer 'inform' or 'update' instead.
Does 'fill someone in' always mean the person missed something?
Not always, but the idea is that one person has information the other person doesn't have yet. Sometimes the person is new to a project, or they simply weren't involved before — they don't have to have been physically absent for 'fill someone in' to be the right choice.
Can I use 'fill in' to talk about myself getting information, or only about giving it to others?
The object of 'fill in' is always the person receiving the information, so if you want to talk about yourself, you'd say 'Can you fill me in?' — with yourself as the object. You can't use it to describe yourself actively finding information on your own; in that case, you'd say something like 'catch up on' instead.
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