We have in error deducted pension contributions for an employee and run and paid payroll. how do I sort this out. No monies have been paid to the pension company?

Thank you for the prompt reply, @Sallymobcad. I'll provide the steps you need to delete a pay run in QuickBooks Online (QBO) Advanced Payroll. 

Before you can delete a pay run, you'll have to unlock it first. Here's how:

1. Look for the pay run in question in the Pay Runs screen.
2. Tap Pay Run Actions then hit Unlock.
3. Type in a reason for this action, then press OK.

To delete a pay run, follow the steps below:

1. Move to the pay period in question. 
2. Select Delete Pay Run on the right side of the page.
3. Tap Delete to confirm.

See this article for the steps on how to opt an employee out of a pension scheme: Opt out of a pension scheme in QuickBooks Online Advanced Payroll.

I suggest you keep this article for reference: QuickBooks Online Advanced Payroll hub. It contains every related article for QBO Advanced Payroll, in case you need them in the future. 

Tag me in a comment below if you have other questions about QBO Advanced Payroll. I'll get back to you as soon as I can. Have a nice day!