Thanks for being a member of the QuickBooks family. I'll be happy to assist with this. QuickBooks Online offers two great payroll services, Standard Payroll and Advanced Payroll, that let you manage your employees’ wages efficiently. That being said, entering paychecks with a date prior to when you started using QuickBooks Online payroll is not an integrated feature of the system. As you mentioned, the available option is to enter current year to date amounts if you've started using the QuickBooks Online payroll service after January 1 of the calendar year and if you’ve already run payroll using another system at least once since January 1.
To know more about QuickBooks Online payroll, check these community pages:
Feel free to reach out if you have any other questions.