The PDA is a promise. The FDA is where agencies lose money.

A port agent's economics fit on one page. The principal asks what a call will cost. The agent answers with a proforma disbursement account: port expenses in section A, miscellaneous in section B, agency fees in section C. The principal remits against it. The call happens. Then the final disbursement account tells the principal what it actually cost.

The PDA is a promise. The FDA is a reckoning. Everything an agency earns or loses on a call lives in the difference between the two.

How the gap opens

The PDA is built from the tariff and the agent's experience. Pilotage by GRT. Tugs by the hour and the number of tugs. Launch hire, fresh water, crew transport, garbage, agency fee. It is usually right on the big lines because the big lines come from a published tariff.

The FDA is built from vendor invoices. And vendor invoices arrive the way vendor invoices arrive: by email a week later, as a photo on WhatsApp, in a stack from the port authority at month end. Each one has to be placed against the line it belongs to, at the price actually charged, billed to the right party.

The gap opens in three ways:

1. A bill arrives and nobody places it. It sits in an inbox. The FDA goes out without it. The agency eats it, or sends a supplementary invoice weeks later and looks disorganised.
2. A bill is placed at the quoted figure, not the actual one. The tug company charged for a third hour. The line says two. The margin on that line is fiction.
3. A bill is placed against the wrong party. Fresh water was for the owner's account, not the charterer's. It goes on the principal's FDA, gets disputed, and gets settled at a discount to make the argument stop.

None of these is a big number on its own. Across a hundred calls a year they are the difference between an agency that makes money and one that does volume.

The job card is the fix

The instrument that closes the gap is old: the job card. One line per service, with the quoted figure, the buy figure from the vendor's bill, the sell figure to the principal, the profit or loss on the line, and who pays. Agents have kept job cards for as long as there have been agents.

The job card was fine. Keeping it current while the bills came in from six directions was not.

That is a reading and matching problem, which is exactly the kind of problem that can now be handed off. Each vendor invoice, as it arrives, is read: vendor, amount, vessel, service. It is proposed against the line it belongs to. A person verifies it. The buy figure replaces the quoted one. The line tints as the bill is booked, approved and paid, so anyone looking at the card sees the current P/L, not last week's.

When the call is over, the FDA is the job card, printed.

What this changes about the PDA

Once the job card is kept current on every call, the PDA gets better too, because the agency finally knows what things actually cost. The next PDA for the same port, the same tug company, the same launch operator, starts from real buy figures rather than the tariff and a memory.

That is the quiet compounding in agency work. The FDA teaches the PDA, if anyone is keeping the record.