Has escrito mal tu apellido en el formulario.

Has escrito is the present perfect of escribir. In Spain, this tense is very commonly used for actions that happened in a time period still connected to the present, especially when the result matters now.

So Has escrito mal tu apellido en el formulario suggests:

• you wrote your surname incorrectly
• and that mistake is relevant now, because it is still on the form

In many parts of Latin America, speakers might more naturally say Escribiste mal tu apellido en el formulario in the same situation.

It is the present perfect, formed with:

• haber in the present: has
• past participle: escrito

So:

• yo he escrito
• tú has escrito
• él/ella ha escrito
• nosotros hemos escrito
• vosotros habéis escrito
• ellos han escrito

The verb escribir has the irregular past participle escrito, not escribido.

Because Spanish forms the present perfect with the auxiliary verb haber, not ser or estar.

So to say you have written, Spanish uses:

• has escrito

not:

• estás escrito
• eres escrito

Those are incorrect here.

Here mal means incorrectly or wrongly.

It modifies the verb has escrito, so it tells us how the person wrote the surname.

• Has escrito mal tu apellido = You wrote your surname incorrectly

Its position is natural after the verb phrase:

• has escrito mal

Spanish often places adverbs like mal after the verb.

Because in Spanish, escribir mal + something is a normal way to say that something was written incorrectly.

Examples:

• Has escrito mal tu nombre
• He escrito mal la dirección
• Habéis escrito mal el número de teléfono

It is a very common and idiomatic pattern.

Because tu without an accent is the possessive adjective meaning your.

• tu apellido = your surname

Tú with an accent is the subject pronoun meaning you.

• Tú has escrito mal tu apellido

So:

• tu = your
• tú = you

The sentence uses tu because it is showing possession.

Spanish often omits subject pronouns because the verb ending already shows who the subject is.

• has escrito already tells us the subject is tú

So:

• Has escrito mal tu apellido is completely normal
• Tú has escrito mal tu apellido is also possible, but it adds emphasis or contrast

For example, you might say Tú has escrito mal tu apellido, no yo to stress you.

En el formulario means on the form or in the form, depending on context.

It is made from:

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

Spanish usually uses the definite article more often than English does. Even where English might simply say on a form or on the form, Spanish often naturally says en el formulario if the form is understood from the situation.

Also, en + el contracts to en el.

Because en is the normal preposition for writing information in a document, form, box, list, or space.

So Spanish says:

• en el formulario
• en la solicitud
• en el documento

Sobre usually means on top of physically, which does not fit the idea here.

Apellido means surname, last name, or family name.

For an English speaker:

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

In Spain and many Spanish-speaking countries, people commonly have two apellidos, so in real-life contexts apellido can refer to one surname or surnames in general, depending on the situation.

You could be understood, but apellido is the normal and most natural word, especially in Spain.

So on forms and in everyday speech, apellido is what you should expect and use.

Examples:

• Escribe tu apellido
• ¿Cuál es tu apellido?

The given order is the most natural:

• Has escrito mal tu apellido en el formulario

But Spanish can move parts around for emphasis.

For example:

• En el formulario has escrito mal tu apellido
• Tu apellido lo has escrito mal en el formulario
  This is more marked and sounds more emphatic.

For a learner, the original version is the safest and most natural.

Yes, it can. On its own, it often sounds like someone is pointing out a mistake:

• Has escrito mal tu apellido en el formulario

Depending on tone, it could be:

• neutral and helpful
• mildly reproachful
• direct or corrective

If someone wanted to sound softer, they might say something like:

• Creo que has escrito mal tu apellido en el formulario
• Parece que has escrito mal tu apellido en el formulario

That adds politeness or uncertainty.