Hay que escribir bien el apellido en el formulario.

Hay que + infinitive is a very common Spanish structure meaning it is necessary to..., you have to..., or one must....

So Hay que escribir bien el apellido en el formulario means something like:

• You have to write the surname correctly on the form
• The surname must be written correctly on the form

It is impersonal, so it does not name a specific person.

Because hay que is more general and impersonal.

• Hay que escribir bien el apellido = this is a general instruction for anyone filling in the form.
• Tienes que escribir bien el apellido = you specifically have to write the surname correctly.

On forms, notices, and instructions, Spanish often prefers hay que because it sounds less direct and more like a general rule.

After hay que, Spanish uses an infinitive.

Pattern:

• hay que + infinitive

Examples:

• Hay que estudiar
• Hay que esperar
• Hay que escribir bien el apellido

So escribir stays in its basic form, just like to write in English.

In Spanish, a singular countable noun usually needs an article or another determiner.

So:

• el apellido = the surname
• tu apellido = your surname
• un apellido = a surname

Saying just apellido here would sound incomplete.

In this sentence, el apellido refers to the surname that has to be written on the form, so the definite article sounds natural.

They are not the same:

• nombre = first name / given name
• apellido = surname / family name

So if your name is John Smith:

• John is your nombre
• Smith is your apellido

This sentence is specifically talking about the surname, not the first name.

Here bien means something like properly or correctly.

So escribir bien el apellido means:

• write the surname correctly
• make sure the spelling is right

It does not just mean having nice handwriting. In this context, it usually means entering the surname accurately.

Because bien is modifying the verb escribir.

• escribir bien = to write well / correctly

This word order is very normal in Spanish. Spanish adverbs often come after the verb.

You could also hear similar patterns like:

• hablar bien español
• pronunciar bien una palabra

Because en means in / on, and that is what fits with a form.

• en el formulario = on the form / in the form

A form is treated like the place or document where the information is written.

Al formulario would mean something more like to the form, which does not work in this context.

Good question. In Spain, people commonly have two surnames: a first surname and a second surname.

But Spanish can still use the singular apellido in a general way when talking about surname information.

Depending on the context, a real form in Spain might say things like:

• primer apellido
• segundo apellido
• apellidos

So this sentence is grammatically fine, but in a real Spanish form you may often see apellidos or separate spaces for each surname.

Yes. That is perfectly correct.

• bien = well / properly / correctly
• correctamente = correctly

Both work, but bien is more common and more natural in everyday Spanish. Correctamente sounds a little more formal.

Yes, hay que is fixed in this structure.

The hay here comes from haber, and in this impersonal expression it stays as hay no matter who the instruction applies to.

So you say:

• Hay que estudiar
• Hay que rellenar el formulario
• Hay que escribir bien el apellido

Never han que.

Yes, that is a good natural translation.

Even though the Spanish sentence literally uses an active structure with hay que escribir, English often expresses the same idea in different ways:

• You have to write the surname correctly on the form
• The surname must be written correctly on the form
• Make sure the surname is written correctly on the form

All of these can match the Spanish meaning, depending on style and context.