As of January 1, 2013 the IRS have not yet released Publication 15 – Employer’s Tax Guide. This booklet typically includes the tax withholding rules as well as percent method withholding tables some use to update their computer withholding.
In the interim the IRS have released Notice 1036 which includes the social security limits and rate as well as percent method withholding that is presently in effect as of 1/1/13. Important: These rates may change as the government votes on pending tax legislation so be sure to check back with the IRS and update any rates as required.
IRS Notice 1036: Early Release Copies of Percent Tables for Income Tax Withholding for 2013 and IRS
