What is an extension?

[jose_m_verduzco]

can my car be added?

[CarolynM]

An extension allows you to delay the filing of your tax returns. The due date is April 15, 2019.

If you have already filed your tax return and want to add your car, you will file an amended tax return.

Since it appears you are self-employed, you can deduct the expenses for your car to the extent it was used for your business. 

For more information, follow these link:

What to Include with Amended Tax Returns 

How to Amend 

Tips to Amend

IRS on 1040X

[Val Perry]

How do I submit an extention

[VictoriaD75]

The document to file an extension can be found in Other Tax Situations in TurboTax. See the link below:

How to File an Extension