If a subcontractor has no payment plan, the contract is placed as a single sum in the month it was created. You can distribute it across the months directly in the grid in the Liquidity module.
How to do it
Open the Liquidity module in the project and go to the Grid — the table below the overview, where the forecast is distributed month by month. Read more in How to read the liquidity overview.
Find the row for the contract — it sits as one amount in a single month.
Edit the row and distribute the amount across the months in which the work takes place.
Liquidity is updated automatically after the distribution.
This is what it looks like:
Tip: an alternative is to create a payment plan on the contract, even if the subcontractor has not agreed to one. You create such a «fictitious» plan purely to control liquidity — it gives even finer control over when the amounts land. See Withheld amounts and final settlement in the liquidity overview for how a payment plan is structured.