As part of changes to the forthcoming taxation of Child benefit in households where a partner is earning more than £50,000, the HM Revenue and Customs (HMRC) will be expecting some high earning partners to find out if they were claiming child benefit.
Either of such couples will also be able to find out from the Revenue if their partner receive child benefit or earn more than £50,000 a year.
Members of such couples will also be able to find out from the Revenue if their partners receive child benefit, or earn more than £50,000 a year.
But the Tax experts say the changes will breach important principles of the tax system.
It would be gradually reducing the concept of independent taxation and taxpayer confidentiality, because there was no other way of going about it, John Whiting, of the Chartered Institute of Taxation (CIOT) said.
Chas Roy-Chowdhury of the ACCA accountancy body said the Treasury had devised a bad tax that HMRC were made to implement. It is a bad idea to tax an individual who is not receiving the benefit. The new tax starts on 7 January 2013 and will affect 1.2 million families.
It is to be levied on those in a household whose "adjusted net income" is more than £50,000 a year and who claim, or any one of them claims, child benefit.
HMRC says it will "expect" couples to discuss their tax and benefits with each other, to find out if the higher earner is liable for the tax, despite the policy of separate taxation of married couples being in place since 1991.
HMRC will also let taxpayers ask for rudimentary information from its records to see whether or not their partners receive child benefit, or have an "adjusted net income" above £50,000, and should be paying the new tax.
This runs counter to the general principle of taxpayer confidentiality, which has been a formal part of the income tax system since 1803. Revealing someone's tax records is currently a criminal offence for HMRC officials.
The relaxation of the two principles is going to happen because otherwise high earners who should pay the tax would be able to claim they were unable to find out if their partner received child benefit, and vice versa.
The HMRC hopes that taxpayers who have to pay the tax will save it the trouble and identify themselves when they are sent forms, as part of an enlarged self-assessment tax system next year.