What is the difference in terms of investigation process for ts/sci vs secret

I have a secret clearance adjudicated 2 years ago. I am being upgraded to ts/sci for a new job. What is the difference in terms of background investigation and process timeline?

Hi. Most likely for your secret clearance you underwent a Tier 3 investigation which is generally an automated background investigation that checks various records. They can be done in about 45 days if there is not a need for an investigator to contact you for more information. For the TS, it will require a Tier 5 investigation which entails an investigator interviewing your neighbors, coworkers, and others, along with you. These are quite a bit more involved and can take several months to complete.

TS-SCI requires a favorably adjudicated SSBI investigation, which involves investigators physically going to and interviewing references, supervisors, co-workers, contacts l, etc. that you refer to on the SF-86 and that they develop themselves.

The investigation process for a Secret is almost entirely automated in comparison and contact to all of the reference types I mentioned above is done via letters they send to them, not physical interviews (a personal interview may be done with you, but not usually).

That being said, with some agencies there are SAP programs that a Secret clearance holder may be granted access to that requires a favorable SSBI, so there are some rare cases where that can technically happen, but it’s not common.

3 months to 3 years is what you can expect. So many different pieces it’s so hard to predict.