In plain English
FAR 52.237-6, Incremental Payment by Contractor to Government, is a contract clause prescribed at FAR 37.304(c), most recently dated Apr 1984. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
We scanned the full clause text and found no sentence directing the contractor to insert this clause into subcontracts. That is a statement about the text, not legal advice: a prime contractor may still flow terms down contractually, an agency supplement (DFARS, VAAR, …) may add requirements, and clauses listed below (if any) may order this clause into subcontracts from the outside.
Where it's prescribed
As prescribed in 37.304(c), insert the following clause in solicitations and contracts for dismantling, demolition, or removal of improvements (a) if the Contractor is to receive title to dismantled or demolished property and a net amount of compensation is due the Government; and (b) if the Contracting Officer determines that it would be advantageous to the Government for the Contractor to pay in increments, and for the Government to transfer title to the Contractor for increments of property, only upon receipt of those payment:
Prescribing reference: FAR 37.304(c).
The official text, verbatim
As prescribed in 37.304(c), insert the following clause in solicitations and contracts for dismantling, demolition, or removal of improvements (a) if the Contractor is to receive title to dismantled or demolished property and a net amount of compensation is due the Government; and (b) if the Contracting Officer determines that it would be advantageous to the Government for the Contractor to pay in increments, and for the Government to transfer title to the Contractor for increments of property, only upon receipt of those payment:
Incremental Payment by Contractor to Government (Apr 1984)
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(a) The Contractor shall perform the work called for under this contract and within _____ days of receipt of notice of award, unless otherwise provided in the Schedule, and before proceeding with the work, shall pay _____ [fill in amount]. Thereafter, the Contractor shall make payment to the Government in the amount and frequency specified in the Schedule. Checks shall be made payable to the office designated in the contract and shall be forwarded to the Contracting Officer.
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(b) Upon the Government’s receipt of each increment of payment, the Contractor shall receive title to such property as the Contracting Officer determines to be fair and reasonable for that increment of payment. Upon receipt of the Contractor’s final payment, all title that has not passed to the Contractor shall vest in the Contractor, unless specifically designated in the Schedule as being retained by the Government. The Government shall not be responsible for the condition of, or any loss or damage to, the property.
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(c) The Contractor shall promptly remove from the site all property acquired by the Contractor. The Government will not permit storage of property on the site beyond the completion date. If the Contractor does not wish to remove from the site any of the property acquired, the Contracting Officer may, upon written request, grant the Contractor permission to leave the property on the premises. As a condition of the granting of this permission, the Contractor agrees to waive any right, title, claim, or interest in and to the property.
(End of clause)