Self-employment company Invoicery Group reports net sales of SEK 161.4 million in May, a decrease of 0.8 percent compared with the same month last year.At the same time, revenue increased from SEK 157 million in April.Rolling twelve months net sales amounted to SEK 1,923 million, corresponding to an increase of 4.9 percent. The number of self-employed workers in Sweden rose to 6,440, up 0.7 percent compared with the previous year.