IHTM31755 - Assessing: deposits: offer to place money on deposit by the taxpayer
If the taxpayer or agent asks you to suggest a suitable sum to place on deposit, you should limit the figure to the minimum amount of tax likely to be payable. Do not include tax which has not yet become due, such as future instalments.
If the taxpayer or agent has placed a substantial sum on deposit that is clearly more than the tax liability, refer the case to your manager.
If you receive a payment that you think might be conscience money, speak to your manager.