How do I verify the work quantities a subcontractor reports?

Short answer

Compare the reported quantity against the contract bill of quantities, line by line.
Have the quantity actually built measured on site, together with the technical inspector.
Check the site journal to confirm the stage really was signed off on the days reported.
Cross-check the matching material consumption — real blockwork square metres imply real blocks and mortar used.
Approve the work statement only for the measured and confirmed quantity, not the requested one.

Law 10/1995 on construction quality — execution must be documented, and the technical inspector checks the work against the verified technical design.
Fiscal Code, Art. 281(7) — for construction and assembly services the taxable event arises when the work statement is issued or, per the contract, when the client accepts it. Whatever you accept becomes payable.
Government Decision 907/2016 — for publicly funded projects, the bill of quantities and the cost estimate per work category are the benchmark reported quantities are measured against.
Accounting Law 82/1991 — costs are recorded against supporting documents, so a work statement must reflect quantities genuinely executed.

Example: the masonry subcontractor reports 480 m² for the ground floor, but the bill of quantities says 430 m². On-site measurement confirms 436 m² — the gap came from door and window openings not deducted. The statement is approved for 436 m²; at 55 RON/m² that avoids 2,420 RON.
Example: on electrical works, the 2,100 m of cable reported is compared with the routes in the design and with the delivery notes for cable received on site (1,850 m). The gap is settled before approval, not at final account.

Approving a work statement on a declared progress percentage rather than measured quantities.
Not deducting openings — doors, windows, stairwells — from the reported areas.
Signing the statement without the technical inspector, then having no way to dispute the quantity at handover.
Checking quantities only at final account, once the subcontractor's crew has already left the site.

The contracted quantity per stage and per subcontractor sits next to the reported one in the Subcontractor Management module.
Work statements are generated from stages confirmed in the daily journal, not from what was reported verbally on site.
Photos stay attached to the day the stage was confirmed — the evidence stays in the project file.
The history per subcontractor shows how often reported quantities were corrected on verification.