QB Issue Resolution:

QB keeps purchases and sales separate, so you can not really do that kind of contract management.  QB is accounting.

You can create an estimate listing the project requirements and create a vendor PO for those items, and in QBO+ you can turn on billable expenses so the items purchased from the vendor can be moved to the customer invoice.

But that is as close as it gets.

Contract management like you are asking is best done in spread sheet, with one page a summary, bringing totals forward from a purchases and a sales detail page.  Or get  a dedicated contract management software package.

Resolution for Issue 'How to register advance payments and subsequent collections' available: Yes (Solved).
Source: Intuit Community forum.

How to register advance payments and subsequent collections: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for advance payments
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Error Recovery for advance payments [Canada]
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