Thanks for reaching out, @mvoschin.

Happy to help you create a previously written check in QuickBooks Desktop. I'd like to gain some additional insight into your question. Are you referring to a payroll check or a vendor check? Is the Check Number field greyed out or what happens when you click on it? Once I know this information I'll be able to get you back to business in no time.

In the meantime, I suggest checking out this awesome article: How to edit check or paycheck numbers

I look forward to hearing from you again. I'll be here to help. Have a great day!