Số tài khoản ở trong biểu mẫu.

In Vietnamese, the head noun often comes first, followed by a noun that specifies it.

• số = number
• tài khoản = account

So số tài khoản literally looks like number account, but in natural English we reverse it and say account number.

This is very common in Vietnamese:

• số điện thoại = phone number
• số nhà = house number
• thẻ căn cước = identity card

So the Vietnamese order is normal; you just should not translate it word-for-word into English.

Tài khoản means account. Depending on context, it could mean:

• a bank account
• a user account
• an online account
• some other kind of registered account

By itself, số tài khoản usually means account number, often a bank account number if the context is financial. Vietnamese often relies on context more than English does.

Vietnamese does not have articles like a, an, and the in the same way English does.

So Số tài khoản ở trong biểu mẫu could mean:

• The account number is in the form
• An account number is in the form

Which one sounds best depends on context. Usually the situation tells you whether the noun is specific or general.

They are separate words, but they often work together.

• ở can mean at / in / located at
• trong means inside / in

Together, ở trong means something like is inside / is in.

So:

• Số tài khoản ở trong biểu mẫu. = The account number is in the form.

In everyday Vietnamese, speakers may use:

• ở trong
• just trong
• just ở

depending on style and context.

Yes, in some contexts you can.

• Số tài khoản ở trong biểu mẫu sounds like a full clause: The account number is in the form.
• Số tài khoản trong biểu mẫu can sound more like the account number in the form, which may be a noun phrase rather than a complete sentence, depending on context.

So if you want a clearly complete sentence, ở trong is helpful.

Yes, trên biểu mẫu can also be possible, and this is a very natural question.

• trong biểu mẫu = in the form, focusing on the form as a contained set of information or fields
• trên biểu mẫu = on the form, focusing on the physical or visual surface of the form

English usually says on the form, but Vietnamese can use either depending on how the speaker conceptualizes it.

So:

• Số tài khoản ở trong biểu mẫu = the account number is in the form
• Số tài khoản ở trên biểu mẫu = the account number is on the form

Both can work, but they emphasize slightly different viewpoints.

Biểu mẫu means form, especially an official or structured form used for filling in information.

It often refers to documents with fields or boxes to complete.

Related words:

• mẫu = form / template / sample
• đơn = application/form, often for official requests
• biểu mẫu = a formatted form, often administrative or business-related

So biểu mẫu sounds fairly formal and administrative.

Vietnamese often does not use a verb equivalent to English to be in the same way.

In this sentence, ở does the job of expressing location:

• ở = to be at / to be located in

So Số tài khoản ở trong biểu mẫu literally works like:

• Account number located in form

In natural English, that becomes:

• The account number is in the form.

So there is no missing verb; ở is already doing important grammatical work.

Yes, it is normal.

The structure is:

• Số tài khoản = subject/topic
• ở trong biểu mẫu = location phrase

So the sentence is basically:

• [The account number] [is in the form].

This is a very common Vietnamese pattern:

• Cuốn sách ở trên bàn. = The book is on the table.
• Tên tôi ở trong danh sách. = My name is in the list.

Yes, the meaning is close, but the focus changes.

• Số tài khoản ở trong biểu mẫu.

  • Focuses on the account number
  • Roughly: The account number is in the form

• Trong biểu mẫu có số tài khoản.

  • Focuses on what exists in the form
  • Roughly: There is an account number in the form

So the two sentences are related, but not identical in emphasis.

Yes, it is grammatical and understandable.

However, depending on context, a native speaker might choose a slightly different version, such as:

• Số tài khoản nằm trong biểu mẫu.
• Trong biểu mẫu có số tài khoản.
• Số tài khoản ở trên biểu mẫu.

The best choice depends on what you want to emphasize:

• location of a known item
• existence of the item
• physical placement on a page
• information contained within a form

So your sentence is fine, but Vietnamese offers several natural ways to express closely related ideas.

A learner may especially want to watch the tones:

• số — rising broken tone
• tài — falling tone
• khoản — falling-broken/heavy contour depending on dialect
• ở — broken rising tone
• trong — level tone
• biểu — dipping/rising contour depending on dialect
• mẫu — broken rising tone

For an English speaker, the most important point is that tone is part of the word, not just emotion or emphasis. If you change the tone, you may change the word.

It is usually best to learn the whole phrase aloud:

• số tài khoản
• ở trong
• biểu mẫu

rather than trying to memorize each word in isolation.