IRS Form 3922 Transfer of Stock Acquired Through an Employee Stock Purchase Plan Under Section 423(c) is for informational purposes only and isn't entered into your return.
Keep the form for your records because you’ll need the information when you sell, assign, or transfer the stock.
When you dispose of the stock, you’ll receive IRS Form 1099-B Proceeds From Broker and Barter Exchange Transactions. This needs to be reported on your tax return. The information on Form 3922 will help determine your cost or other basis, as well as your holding period.
The IRS doesn’t recognize income when you exercise an option under an employee stock purchase plan. However, you must report a gain or loss on your tax return for the year you dispose of the stock.
There are two scenarios. Your employer (or its transfer agent) has recorded a first transfer of legal title of stock you acquired pursuant to your exercise of an option granted under an employee stock purchase plan. Or the exercise price was less than 100% of the value of the stock on the date shown in box 1 or was not fixed or determinable on that date.
You can find more information at IRS Publication 525 Taxable and Nontaxable Income.