Once an estimate is converted to a job, you have the option to add new cost items via a Change Order or a Builder Gain / Loss.
To add a new cost item, navigate to Jobs > select the relevant Job > Job Financials > Budget and scroll down to the relevant cost code. Click on the Cost Code to expand the details, and click on 
.
Fill out the pop-up menu with your new Cost Item Name, the Cost Type and your UOM, then click Save.
To add a $ amount to the new cost item, select the tick-box on the left-hand side and click on the Gain / Loss or Change Order button.
A Builder Gain / Loss would be used if the builder chose to use a different supplier or subcontractor and there was a change in the price. This difference will not be passed on to the client. This will reduce or increase the profit the builder is making on the job.
A Change Order would be used if the client changed their mind about a Cost Item. For example, they decided after the estimate was complete that they wanted a rainwater tank installed. This difference will be passed on to the client.
Once the new Cost Item is created, Bills can be added against this line item.