SmartAsset and Yahoo Finance LLC may earn commission or revenue through links in the content below.A large, one-time conversion can create a significant upfront cost, which is why some investors choose to convert smaller portions over multiple years to manage the tax impact.When you convert pre-tax savings to a Roth IRA, the converted amount becomes taxable in the year of the transfer. This added income can increase your federal tax bill, move you into a higher tax bracket and affect other calculations tied ...