There were 7,536 sale and purchase agreements for all building units.
The Land Registry said the figures represent a 16.1% on April but up 24.3% compared to a year ago.
The total consideration for sale and purchase agreements in May was $66.8 billion, down 24.1% on April but up 37.1% year-on-year.
Among the sale and purchase agreements, 5,732 were for residential units, an 18.8% decrease on the previous month but 25% more year-on-year.
The total consideration for residential units was $53.6 billion, down 23% compared with April but up 30.9% compared with last May.
The public made 459,409 land register searches during the month.
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