Sage just released their form 941 form update. If you are actively using Sage 100 (aka MAS90/MAS200) payroll this is something that should be installed.
If you are not actively using payroll then this does not apply to you.
This update is compatible with the following versions of Sage 100 ERP (MAS 90 and 200):
5.00.1 (already included with 5.00.2.0)
4.50.0.00 - 4.50.5.0 (already included with 4.50.6.0)
4.40.0.0 - 4.40.0.10
4.30.0.18 - 4.30.0.23
Note: Using the Help/About menu item will display the version of Sage 100 installed to your computer. Prior to the install of Sage 100 ERP Payroll and 941 Update 2013:
For version 4.30.18-4.30.0.23, 4.40.0.0-4.40.0.10 and 4.50.0-4.50.04 you must have the 2012 IRD and2013-Q1 Tax Table installed.
For version 4.50.5.0 and 5.00.1.0 you must have the 2013-Q1 Tax Table Update installed.
For version 2013 (5.00) you must have Product Update 1 for Sage 100 ERP 2013 (5.00.1) installed.
I've downloaded this file so you won't have to wade through the Sage portal to find it. By clicking the link below you can download it to your computer.
https://www.dropbox.com/s/9y3d3kvxew662ir/sage100erppayrolland941update2013.exe
If you prefer you can first login to Sage's customer portal and then click this direct link:
http://goo.gl/hHjgc
More information on what is included is available here:
https://partners.sagenorthamerica.com/irj/go/km/docs/sageKM/Sage%20MAS%2090%20and%20200/Assets/Sage%20100%20ERP%20Payroll%20and%20941%20Update%202013.pdf