Experts from financial firm Baker Tilly have shown that HMRC could be in for a headache following the new child benefit rules.
It is thought up to one million letters will be issued during November to families affected by child benefit changes.
The tax return deadline this year if you wish to send in a paper copy is 31st October.
HMRC has offered 'Direct Sellers' a chance to come forward about their tax affairs.
There is one week left for 40 per cent tax rate payers or above to take part in the Tax Return Initiative.