Here are the instructions to request your tax transcripts online for a mortgage application.
It takes about 10-15 min and you will need a credit card number, a mortgage loan number or something of that sort as part of the security verification process.
Getting tax transcripts for a mortgage is FREE, credit card is for security purpose only.
Below is the step by step screen shots.

IRS Web Link:  https://www.irs.gov/individuals/get-transcript

Step 1: Click on "Get Transcripts Online"

Step 2:  Create a new Account, this will take you about 10+ minutes and can be a lenghty process as they will need specific information from you about your credit report, i.e. "You have a car loan from 2010, which bank is that from", and then it will give you 4 answers.  Some of the answers will be correct, sometimes none of the answers will be correct.  Read VERY Carefully!

Step 3:  Once you are in, the following screen will pop up, you DO NOT need a "Customer File Number".

Step 4:  We recommend that you download (AS PDFs)  ALL available "Return Transcripts" for last 3 years, these are copies, in IRS format, of your Federal Tax Returns.  We also recommend you download ALL "Wage & Income Transcript" for last 3 years as well.

Step 5:  Save the PDF's onto a secure area of your desktop, and keep these for 5 years for your records.

Step 6:  Upload the PDF's  1st Choice Mortgage through secure Web Portal, link HERE