Quickbooks enables you to submit your VAT on line, provided you have regsitered with HMRC a a gateway user linked to the relevant company. You input your gateway credentials into quickbooks and then you can file your VAT via quickbooks.
So step 1 is to sign up for gateway account at HMRC.gov.uk and make sure you are opting to file VAT on-line. You will need your VAT number, last submitted retrun box 5, so make sure you have info to hand.
Step 2 is that once you are enabled for VAT filing you can file your VAT via quickbooks or the HMRC VAT portal.
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