Hi there, keikiclubhouse.

QuickBooks Payroll update error 15243 occurs when there's an interruption while doing an update in QuickBooks Desktop. Following are the lists of reasons for this error:

• The update is not complete
• Due to damaged QuickBooks FCS
• The QuickBooks FCS is not responding

Please check out the solutions on how to fix this:

Solution 1: Repair QuickBooks

1. On your keyboard, press Windows+E to open the Computer window.
2. Click Uninstall or change a program.
3. Select QuickBooks.
4. Once QuickBooks is selected, click Uninstall/Change.
5. In the QuickBooks Installation window, click Next, select the Repair radio button, click Next then click Repair.
6. Click Finish.

Then, re-validate Service Key. Here's how:

1. Click Employees > My Payroll Service > Manage Service Key.
2. The QuickBooks Service Keys will open.
3. In the QuickBooks Service Keys window highlight the current payroll subscription and select Edit.
4. Click Next through to Finish or click OK. QuickBooks will re-validate the payroll subscription.
5. When the validation is complete, the tax table will update to the correct version.

Solution 2: Install all available Windows Updates

1. Click on the Start button.
2. In the search box, type in Update and press Enter.
3. The Windows Update dialog box will appear on your screen.
4. Click the Install Updates button if there are available.

The above solutions will surely help you fix this payroll update error 15243 concern. 

Please keep me posted on how the steps work. I want to make sure everything is taken care of for you.