You can do that if you want to. The way you fill out your W-4 or W-4P does not dictate how you will file your tax return. It just affects how much tax is withheld from the retirement income. The total amount of income and amount of tax withheld are reconciled when you prepare your tax return. And....for many pension plans, retirement plans, etc. you can just choose a percentage that you want to have withheld for tax.