How to maintain a payroll app?

Welcome to QuickBooks Community, vimal1.

If you're currently using a third-party payroll provider, you'll want to reach out to their support. They can surely assist you on how to sync it with QuickBooks Online and maintain the integration of the two platforms.

You can also subscribe to the Paybooks which is a supported payroll application of QuickBooks Online. You can search it through the Apps tab. For the detailed steps, you can check this link: Paybooks is now available in the Apps tab.

Keep on posting here if you have more questions. Take care!