i have to rework 12 months of bills to account for vat, how do i do this?

You want to make sure that you have already set up VAT in QuickBooks Online (QBO) before going over to each bill and including its VAT, @penny42.
 

Here’s how to set it up if you haven’t done so yet:
 

1. Go to Taxes and select VAT.
2. Select Set up VAT.
3. Select the month you need to start calculating VAT from.
4. Select your filing frequency for VAT. This is how often you will submit VAT returns to HMRC.
5. Choose your VAT accounting scheme (either Standard or Cash).
6. Enter your 9-digit VAT registration number.
7. If applicable, select the Flat Rate Scheme (FRS) checkbox and enter the percentage and tax registration date.
8. Select Next, and then OK.
 

For more information on managing VAT in QBO, please refer to this article: Set up and manage VAT in QuickBooks.
 

Now, let’s proceed to include VAT on each bill:
 

1. Click the View/Edit option for the specific bill. 
2. Choose either Exclusive of Tax or Inclusive of Tax next to the Amounts are caption. 
3. In the Category details, click on the VAT column for the bill and select its corresponding VAT code.

4. Click Save or Save and close.
 

Furthermore, if you need to adjust VAT in QuickBooks, visit this content: Make VAT adjustments in QuickBooks.
 

This thread will remain open if you have additional questions or need further assistance with managing VAT in QuickBooks. The Community is here to help you.