TTOG4185 | Investigation work: opening under Code 8: payments on account
From HM Revenue & Customs · Technical Teams Operational Guidance
Where it becomes clear that additional tax liabilities arise as a result of the Investigator’s enquiries, the taxpayers should be invited to consider making a general payment on account.
The payment on account should not exceed a reasonable estimate of the additional tax due.
Where the taxpayer does not have the immediate means to make a payment on account, we expect arrangements to be put in place (to realise assets, to bring money back from offshore etc.) as quickly as possible.
If appropriate, a regular instalment arrangement can be arranged.