If you're referring to the entry for income tax deducted (line 437), there's no need to restart. There's a simple entry mistake in the income section of your return. Navigate back to your income entries using the Find button and check each slip you have entered for accuracy.
Also, check for duplicate entries - for example, if you only had one T4 and you see two T4 entries on the T4 Summary page, delete the extra one.