Unfortunately, adding a Form W-2 usually decreases your refund rather than increasing it.
This is because your tax liability is calculated on your total income (after deductions and credits), not on each individual Form W-2. As your taxable income increases, your tax liability increases as well.
In addition, as your taxable income increases, you may lose eligibility for income-based tax credits such as the Earned Income Credit or lose the ability to claim certain deductions.
Please check out the TurboTax FAQ below for detailed examples of what I have described here:
https://ttlc.intuit.com/replies/3798403
