MIRASMIRAS /ˈmaɪræs, -rəs/ noun [uncountable] 
(Mortgage Interest Relief at Source) a system used until 2000, in the UK, by which someone who had a mortgage (=money borrowed from a bank etc to buy a house) was allowed to pay less income tax. The borrower was given tax relief (=the right to pay less tax) on the interest that he or she paid on the mortgage, and this reduced the cost of the mortgage payments.
(Mortgage Interest Relief at Source) a system used until 2000, in the UK, by which someone who had a mortgage (=money borrowed from a bank etc to buy a house) was allowed to pay less income tax. The borrower was given tax relief (=the right to pay less tax) on the interest that he or she paid on the mortgage, and this reduced the cost of the mortgage payments.