In QuickBooks Self-Employed (QBSE), you cannot add a date column for line items on invoices, Christopher. QBSE is designed with basic invoicing features, so it only contains fields like Description, Amount, and Taxes.
However, you can use the Description field to include dates as a workaround. For example, instead of writing "Consulting Services", you could add "Consulting Services (Completed on 10/12/2023)". See the attached screenshot for reference.

This way, you can clearly communicate the relevant dates, even without a specific date column.
QBSE's limited features are designed for freelancers and independent contractors to manage income, expenses, and simple invoices. If you would like to customize your invoice line items with Service Date, consider switching to QuickBooks Online (QBO) for more flexibility.
Please let us know if you have any further questions. The Community team is here to lend a hand.