It really depends on the time between contract and delivery   a couple of days just invoice them, other wise

I would create an estimate

convert that estimate to an invoice when you ship or deliver

Resolution for 'contract and delivery issue: 'What is the preferred way to record a sale in QB after our customer has signed a contract but before our firm has delivered the merchandise?' available: Yes.

The contract and delivery 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 contract and delivery issue yourself by looking for a resolution described in the article. If it is a complex contract and delivery issue or you are unable to solve the issue, you may contact us by clicking here or by using other contract and delivery support options.

For more information about resolving issues related to contract and delivery in Quickbooks/QBO or to get support for the issue 'What is the preferred way to record a sale in QB after our customer has signed a contract but before our firm has delivered the merchandise?', click the link below: