Tom and Mary married on 10 July 2018. They continue to be taxed as single people for 2018.
As single people they pay a total of €10,640 in income tax for the year. Tom paid €9,140 and Mary paid €1,500.
If they had been jointly assessed, they would have paid €8,840.
The difference between the two amounts is €1,800.
As they were married for six months of the year, a refund of €900 is available (€1,800 x 6/12).