You do NOT want to file a "claim of lien" on a job owned by the government. There is probably a payment bond recorded or posted to secure the payment claims of people like you, who have a contract with a sub-contractor, also referred to as a "sub-sub-contractor." A sub-sub-contractor wants to file a claim on the payment bond. There is a law covering State-owned projects and a different law covering bonds on projects owned by the Federal (U.S.) government. You should get in touch with a construction lawyer who knows how to do this, and who has done it before, who can assist you in making your claim on the payment bond. In some cases, your claim can include the money you have to spend on costs and on attorneys fees paid to your lawyer to make the bond claim.
On a public works project, you do not file a lien. You should immediately consult with an experienced construction attorney. There are short time limits on when you are required to provide the notice of nonpayment. Also important is whether you timely provided any required preliminary notices. If for any reason you are not protected by the bond, you still have your contract claim against the subcontractor that hired you. The most important thing is that you do not delay.
If it is a public works project, there is a payment bond in place. If it is a project that involves an agency of the federal government, you can filed a claim against the Miller Act payment bond. The time period for you to file a claim on a Miller Act payment bond is before the expiration of 90 days after your last date of work. If you are approaching that deadline you need to contact the Contracting Officer, ask for a copy of the payment bond, and file a formal claim (sent by certified mail) to the General Contractor and to the Surety within the 90 day period.
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