The contract system of Mercatorio allows for a variety of different contracts to be offered to trading partners or other interested parties. While most trading in the game takes place in open markets, it can sometime make sense to draft more bespoke deals, either to shelter it from the open market or to extend deals past a single trade.
A contract starts as a proposal, either directed at a business partner or open to anyone to undersign. The proposal includes one or more transactions, where the counterparty agrees to collect or deliver products at a given location for a fixed price.
We’re preparing a proposal for a named
counterparty to collect beer from our storehouse at a fixed price.
The parties of a contract are often other gentry, or the government or church of a town.
The Town of Orlebourg is offering a good
price for timber deliveries to the town. Some or all of the timber can
be delivered at any time, from our warehouse or directly from a cart or
ship.
By adding multiple transactions to a contract, we can request pre-payment or a deposit before we produce expensive products that we may not have stable demand.

In this case whoever picks up the contract will have to transfer some money, after which we have time to produce the windows and prepare them for collection. This contract has both timelines for the payment and collection, as well as prestige penalties if one party fails to perform, eg. by not providing the windows as agreed after already pocketing the pre-payment.
A special case of multi-stage contracts is the payment and re-payment of money, aka a loan.

Lumps sums are lent and repaid at a future date, with interest. Failure to repay will cause loss of prestige.
Each transaction in a contract can have a separate timeframe, either defined in absolute dates or relative to when the contract is signed by the counterparty. The timeframe defines a window of time when the delivery or collection should take place.

If the transaction fails, either due to the warehouse owner failing to reserve products or space before the delivery window starts or because the collection or delivery isn’t performed, the failing party may lose prestige.
A special case is a contract with the Church of your town, which sometimes desires donations. A donation is simply a delivery without payment.

If you pick up one of these contracts and fulfil it in time, you gain increased prestige in lieu of monetary benefits.