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How to Choose the Right SIN and Avoid GSA Rejection Blog Feature
John Abel

By: John Abel on March 8th, 2024

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How to Choose the Right SIN and Avoid GSA Rejection

GSA Schedule | 4 Min Read

Professional services, electrical supplies, cloud solutions, power tools – if your company is selling it, GSA (probably) has a Special Item Number (SIN) for it. All contractors part of the GSA Multiple Award Schedule (MAS) program have the ability to add any of the 315 SINs available to their contract at any given time or include any assortment of them in a MAS contract proposal.

That being said, you will want to make sure that it makes sense for your business and that you meet any specific requirements that SIN may have, otherwise you can risk rejection of your GSA Schedule offer or modification. Let's discuss choosing the right SIN for your contract and how you can avoid rejection. 

How to Add a SIN to Your GSA Schedule

Generally, the process to add a SIN to your GSA Schedule contract, or include it within your original proposal, is fairly consistent. However, certain SINs do have certain specific requirements that contractors need to look into prior to submitting an offer or SIN addition modification.

Each industry grouping underneath the consolidated GSA Schedule is divided into its own Large Category – Ex. Large Category F for IT, Large Category J for Security and Protection. Nonetheless, all of these Large Categories all fall under the MAS umbrella.

However, each Large Category has its own reference documentation that is essential for contractors to download and review prior to moving forward with any modification action or contract proposal.

Check to See if Your Special Item Numbers (SINs) Have Specific Requirements

Below are three helpful tips on how to better understand any specific requirements that your Large Category or SIN may have:

  1. Check the MAS Modification Guide to see the requirements for the type of modification you are performing. Page two of the guide will take you to the section you need. Each document that is required in the modification is outlined in detail in the guide. 
  2. Check the Available Offerings and Requirements page. This page is where you will find category specific attachments and templates. Refer to your specific Large Category and SIN on the second half of the page to see if GSA has listed any particular documents that may be applicable to your offerings.
  3. Check the Large Category attachment for your offerings’ SIN. These can be found on You will want to review the first few pages of the Large Category attachment as well as review any additional requirements by searching for the SIN itself in the Large Category attachment. The Large Category attachment will highlight any additional requirements for ordering, technical evaluations, past project write-ups, SIN-specific terms, etc. The Large Category attachment is your best resource for determining if any additional requirements are needed.

How to Determine which Special Item Numbers (SINs) Are Best for Your Company

Once you have reviewed the information contained within GSA’s array of resources, you should be able to accurately determine which SINs are the best fit for your business and which Special Item Numbers you have a viable case to either add to your GSA Schedule contract or include in your MAS proposal.

The most important aspect when it comes to SIN determination is scope. Do your company’s services or products match what GSA outlines as the scope of a certain SIN? This is a question that the Subject Matter Experts (SMEs) at GSA will ask as well when reviewing your modification package or MAS proposal.

GSA may reject your proposed SIN addition or proposal entirely if it is determined to be out of scope. To avoid rejection, it is important to address that issue at the forefront.

How to Avoid Rejection When Proposing or Adding Special Item Numbers (SINs)

Once you have determined which Special Item Numbers are applicable to your company’s offering, you will need to ensure that your documentation is current, accurate, and complete. In order to assist GSA in the review process and avoid potential issues, you will want to make sure that you have double-checked the solicitation requirements and properly address all relevant requirements.

If you are proposing a service-based SIN, past performance substantiation will likely be required meaning there will be a need to pull relevant projects as examples and to complete past project descriptions as outlined in the MAS solicitation.

While products will not typically require past performance descriptions, there may be additional technical requirements such as National Institute of Standards and Technology (NIST) compliance documentation, testing certifications for furniture, certifications related to recycled materials, or additional compliance documents related to specific executive orders and directives.

Everything you need to know prior to submitting a proposal or a SIN addition modification can be found within the MAS Solicitation and your applicable Large Category Attachment(s).

Do You Have More Questions About Special Item Numbers?

Do you have further questions on what may be required for a specific MAS SIN, or are you wondering where your business fits within the consolidated Multiple Award Schedule? Winvale has the expertise and resources to help. Contact us for more information and assistance with determining the right SINs for your company.

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About John Abel

John Abel is Manager of The Winvale Group focusing on government contracting and federal acquisition opportunities for businesses. He is a native of Stafford, Virginia and graduated from James Madison University with his Bachelor's of Arts in History.