Hi, I have an oustanding invoice in a previous VAT period that I either wish to cancel and reinvoice, or credit part prior to payment.Which is easiest for VAT Calcs?

I'm glad you came here for support, joecox.

Both options mentioned are correct. You can either void or delete the invoice or credit partly.

Deleting the invoice will permanently remove the transaction from your company file. Voiding it on the other hand, only cancels the transaction and will keep the invoice number and list it in reports with zero amount.

To delete/void an invoice:

1. Open the invoice.
2. Click More and choose either Void or Delete.
3. When prompted, select Yes.

 If you choose to credit it partly, you can Receive payment the half amount and write a Bad debt for the remaining balance.

Here's how:

1. Go to Sales, then Invoices.
2. Locate the outstanding invoice and click the Receive payment link.
3. Enter the partial amount.
4. Click Save and close.

Once done, you can start writing a bad debt to zero out the remaining balance. Check out this article for a complete instruction: Write off bad debt in QuickBooks Online.

Reach back to me if you have any other concerns. I'd be glad to offer additional help. Have a nice day ahead.