Which tenses take on HAS, HAVE and HAD?

You may be wondering which tenses take on HAS, HAVE and HAD if you are studying English.  It can get a bit confusing!  So let's take a look:

The Present Tense: HAS or HAVE?

Quite simply, for the verb TO HAVE, there are two conjugations: HAS and HAVE.  Notice that the third person singular is the only subject that takes on HAS 

Singular                             Plural

I                   HAVE             We       HAVE

You              HAVE             You     HAVE

He                HAS                They    HAVE

She               HAS

It (my dog)  HAS

The Past Tense: HAD...

What makes English so easy is the fact that its past tenses are all the same.  The past tense of HAVE is always HAD, so it makes it super easy to remember.

Singular                                   Plural

I                      HAD                  We       HAD

You                 HAD                 You      HAD

He                   HAD                 They     HAD

She                  HAD

It (my dog)      HAD                 

Okay, that's easy, but what about the PRESENT PERFECT?

The present perfect is used to express past happenings that continue to the present or relate to the present.  It always takes on an auxiliary verb TO HAVE plus the past participle.  Let's take a look using the verb TO SEE.  To understand when and why we use the present perfect, click here on another post. 

Singular                                         Plural

I                      HAVE SEEN         We       HAVE SEEN

You                HAVE SEEN         You      HAVE SEEN

He                  HAS SEEN            They    HAVE SEEN

She                 HAS SEEN

It (the dog)    HAS SEEN

Notice here that again, the 3rd person singular takes on the verb conjugation HAS.

And what about the PAST PERFECT?

Once again, the past perfect is easy because the auxiliary verb does not change.  It is always HAD + the past participle.  Let's take a look using the verb TO BE in the past participle:

Singular                                               Plural

I                      HAD GONE                We            HAD GONE

You                 HAD GONE               You           HAD GONE

He                   HAD GONE               They          HAD GONE

She                  HAD GONE

It (my dog)      HAD GONE

Reader's Question: "How can I use HAS and HAD in the same sentence?"

I have written about the difference between has and have in a previous blog, and now, to answer a reader's question, we'll take a look at how to use has and had in the same sentence, .  First of all, we have to differentiate between the uses of has and had in English as:
1. verb
2. auxiliary/helping verb
3. past participle. 

1.  HAS & HAD as VERBS

As a verb, has is the 3rd person singular, affirmative conjugation in the present tense:

I have a German Shepard.               
You have a cool pair of boots.
She has wonderful friends.
He has a brand new car.
It has a great view.            
We have two tickets.
They have the same job.

As a verb, had is conjugated in all voices in the past tense:

I had a great time.
You had the same teacher.
She had a job as a researcher.
He had a difficult time finding the address.
It had three bedrooms.
We had a wonderful Christmas.
They had fun surfing at the beach.

Therefore, you can combine the present and past tenses in the same sentence as seen here:

She had a job as a researcher, but now she has a job teaching English.

2.  HAS & HAD as AUXILIARY/HELPING VERBS

Has can function as an auxiliary verb in English in the third person present perfect tense.  Remember the structure of the present perfect is as follows: SUBJECT + HAVE/HAS + PAST PARTICIPLE.  Click here for more about the present perfect.

I have visited them in Hawaii.
You have worked here for a long time.
He has lived in Lisbon for one year.
She has already tried the new récipe.
It has been a beautiful and warm day.
We have traveled to five countries together.
They have just heard the news.

Had also functions as an auxiliary verb in all voices of the past perfect tense.  The grammatical structure is SUBJECT + HAD + PAST PARTICIPLE.  Notice in the following examples how the past perfect takes place duirng the time before the past tense.

I had already learned Portuguese before I moved to Portugal.
You had gotten home before dinner was ready.
He had worked for 10 years at the same company before he changed jobs.
She had sold her artwork before she became famous.
It had been cloudy and rainy before the thunderstorm started.
We had lived in the United States for many years before the economy worsened.
They had already seen other movies by the same director.

Therefore you can combine the present and past perfect tenses to make a sentence using both has and had:

She has worked as a judge for a long time, but before she accepted the position as a judge, she had worked as a law professor for 10 years.

3.   PAST PARTICIPLE

Finally, let's take a look at the verb have:

INFINITIVE: to have
PAST TENSE: had
PAST PARTICIPLE: had

As you know the present perfect takes on a past partciple, so we can combine has and had as follows:

She has had a position at the law firm for ten years.

He has had a difficult time adjusting to the new city.

My dog has had a virus for a couple weeks.

When do I use HAVE and HAS?

"Have" and "has" are both present tense conjugations of the verb "to have," and we use "have" or "has" depending on the subject.  

If the subject is 3rd person, singular, then you use "has."  All other subjects take on "have".  See below:

Singular                                 

1st Person         I have            

2nd Person        You have            

3rd Person       He/She/It HAS        

Plural
1st Person          We have
2nd Person         You have
3rd Person         They have

Ex.

She has a doctor's appointment tomorrow.

They have a long day ahead of them.

My dog has a good temperament.

We both have an iPhone.

My sister has a hybrid car.

Remember that the verb "to have" serves two purposes in the English language:

1. Verb: Of course, as you know, the verb "to have" is used to express possession, as in the examples above and as in "I have a dog, a house and a beautiful family."
2. Auxiliary Verb: "Have" is also used as an auxiliary (or helping) verb when using the present perfect.  (Click here to learn more about the present perfect.)  See below for the grammar construction of the present perfect:

Present Perfect Grammar:

When using the present perfect, we conjugate the verb "to have" in the same way as the present tense as seen above; that is, the 3rd person singular changes to "has."

I/You/We/They + HAVE + past participle

He/She/It            + HAS    + past participle

Ex. 

I have traveled to Paris three times.

He has never seen a James Bond movie!

They have taken the test.

She has tried to help.

We have just finished writing the report.

My dog has already gone for a walk four times today.

They have taken the test.

She has tried to help.