You will need to improve the detail of your record-keeping, to satisfy VAT Regulations. It sounds like you are a retailer, ie: your customers are the general public, unable to recover VAT. In this case, you are entitled to use a Retail Scheme to calculate your output tax. However, you cannot switch between methods for each quarter; you need to choose a method and stick with it. From your comments, you are able to use the Apportionment Scheme (Notice 727/4 at http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageVAT_ShowContent&id=HMCE_CL_000146&propertyType=document)