Use this for work delivered over many months, like an annual contract.

Open Sales, tick Spread over several months and set the month count.

Period = starting month.

Total amount = full contract value.

Mark Collected in full if paid now, or enter the part received and pick the Customer.

NapkinLedger holds the future part aside and moves one slice to income each month, so one big deal does not inflate a single month. Add a Reference and press Record it.