If I do a conversion from IRA to Roth why am I assessed a penalty when the taxable amount on the conversion is not due until April, not when the conversion occurred ?

Why, If I convert $25000 in January from an iRA to a Roth, in the turbo tax program I am assessed a penalty for not paying taxes throughout the year when taxes are not due on a conversion until the filing. how can the turbo ta program be corrected.