I cannot seem to find the VAT Adjustment I made in order to delete it - can anyone help please?

I can be of assistance with deleting a VAT adjustment you've made in QuickBooks Online (QBO), helen. This way, we can correct whatever adjustment we've made to keep your records accurate.

When we create an adjustment, these transactions are posted to the account where you're creating it for. To delete it, we can go back to the posting account and delete it. Please know that once you remove them, you’ll no longer see them when you review your VAT return on the Taxes screen. You can follow the steps below for complete guidelines: 

1. Go to the Gear icon and select Chart of Accounts (COA).
2. Locate the income or expense account where the adjustment has been posted.
3. Hit the Run report under the Action column.
4. You can also sort the Report period to easily locate the transaction.
5. Select the transaction to expand and hit the Delete button.
6. Then, click Yes to confirm.

Moreover, you can scan this article to learn about filing your VAT and recording its payments: File your VAT return and record VAT payments in QuickBooks Online.

Let me know if you require additional help with taxes. The Community is always available to lend a hand for help. Take care!