I am farming so claim VAT back how dose it work when I sell lambs at zero rate and are charged commission selling the lambs and vat?

I can help you in recording this transaction, @hayes682.

You can create a sales receipt or an invoice and deposit it to the Undeposited Funds account for the sale. When you record this to your bank account, enter the commission under Add other funds to this deposit.

If this is a deferred payment, you can use an Invoice. For immediate payment, use Sales Receipts.

To create an invoice:

1. Go to the + New and choose Invoice.
2. Complete the fields with necessary information.
3. From the Deposit to drop-down, choose the Undeposited Funds account. 
4. From the VAT column, choose 0.00% Z from the drop-down menu. This is a zero rate VAT. They are taxable for VAT, but the VAT rate is zero percent. 
5. Select Save or Save and send.

To create a Sales Receipt:

1. Go to the + New and select Sales Receipt.
2. Add all the necessary information.
3. From the Deposit to drop-down, choose the Undeposited Funds account. 
4. In the VAT column, choose 0.00% Z from the drop-down menu. This is a zero rate VAT. They are taxable for VAT, but the VAT rate is zero percent. 
5. Click Save and close.

Check this article for more information: Should I use an invoice or a sales receipt?.

From here, you can now create a bank deposit and add the commission under Add other funds to this deposit:

1. Go to the + New and select Bank Deposit.
2. From the Account drop-down▼menu, choose the account you want to deposit the money into.
3. Select the box for this payment.
4. Enter the amount of commission as a negative figure under Amount (e.g. -100).
5. Select Save and close or Save and new.

Here's the record and make Bank Deposits in QuickBooks Online article for more information. 

I'm always here if you have any other concerns. Keep safe and have a great rest of the day!