I see that you've posted the same inquiry concerning writing checks for your vendors in your QuickBooks Online account in the Community thread.

I suggest visiting my peer response for more details in regard to your query: https://quickbooks.intuit.com/learn-support/en-us/reports-and-accounting/re

Once you have the checks prepared, you can proceed with printing them. Step-by-step instructions for this process can be found in this article:  Print a check in QuickBooks Online.

Let me know if you have additional questions about your vendor checks, The Community will address them once you get your response. Keep safe!