Real-time advance wharfrent calculator so C&F agents can verify charges before committing, not after.
The port's billing system creates permanent entries — there was no way for a C&F agent to estimate wharfrent charges before committing to them. That caused billing disputes, excessive cargo dwell time, and repeated trips to the counter just to check a number.
C&F agents at Mongla Port who need to know the expected charge before final submission, and — indirectly — the billing desk, which now fields fewer disputes over surprise totals.
Had to match the port authority's actual slab/VAT/levy rules exactly — a wrong estimate is worse than no estimate. No access to the port's internal billing database, since this is an advance estimator, not a system of record. Output had to be print-ready A4, because C&F agents still work from paper.
Slab-based charge computation, VAT and levy calculation, inside/outside cargo split, hoisting charge auto-calculation, print-ready A4 output.
Plain JavaScript/HTML/CSS over a framework — the whole app is one calculation form, and a framework would add build tooling for no real benefit. Deployed as a static PWA on Cloudflare Pages: no hosting cost, works offline, matches how the billing desk actually operates.
Getting the slab/VAT/levy math to match the port authority's real billing system exactly — any mismatch makes the estimate actively misleading to the agents relying on it, worse than not having the tool at all.
In daily use by C&F agents at Mongla Port to verify expected charges before final submission — the evidence is that it's still running there today, not a one-time pilot.
A tool doesn't need a backend to be a real system its users depend on daily — client-side logic was enough because the estimate never needed to persist past the moment it's checked.