You are legally bound (upon registration) to return the output tax charged, minus input tax incurred to the HMRC. How simple is that? Many businesses fall foul of the Customs Office, due simply, to poor and incomplete records. Using KPB Monarch systems, VAT is not just recorded but real time budgets and forecasts which will always maintain funds to discharge liabilities to Customs. Always remember that the VAT charged is not your money, it should never form part of any forecast or budget. In accountancy terms it can only appear on the balance sheet as owing or owed.
Be aware that the Chancellor takes a very dim view of businesses manipulating VAT. I would remind those registering for VAT that you are to become a custodian of the Queens Money and her Chancellor will seek all within his or her power to recover such money, which should, by law, be in the treasury account. Tread carefully when considering voluntary registration under the threshold, currently 85k.