Children who pay mortgages for their parents will not benefit from the new mortgage relief scheme unless they share ownership, the Commissioner of Inland Revenue said yesterday. Wong Ho-sang was answering queries from some of the 500,000 taxpayers who will benefit from the tax deduction on mortgage interest payments. Each can claim an annual maximum of $100,000 per mortgage to cover the cost of borrowing from banks for any five years. Mr Wong said the scheme only applied to genuine home owners. 'For a cohabiting couple, I suggest they get married so they can claim the benefit by using a married couple's combined tax form, which says the benefits can be shifted between one and another,' Mr Wong said. Since the benefit could only be given to a taxpayer who owned a flat, children or spouses who paid mortgages for their parents or partners would not be eligible. He said inspectors would check whether the scheme was being abused. The department is reviewing whether it requires extra staff to investigate suspected tax evasion. Mr Wong said there were about 2,000 such cases in the past financial year, involving $2 billion.