Expansion into North America by for EML Payments is yielding a rapid lift in a range of business and financial metrics, although its investment program is filtering through more slowly to the bottom line.The business model may yet unlock plenty of cash, with EML counting on "breakage" on stored balances to fill out its balance sheet.Net profit for EML more than doubled to A$1.4 million over the half year to December 2016 from $633,000 over the same period in 2015. Revenue more than trebled to $32.4 million from $10.6 million.EML managing director Tom Cregan said it generated 85 per cent of revenues offshore over the half, while 90 per cent of revenues "were recurring in nature".Gross debit volume reached $1.9 billion, a four-fold increase.EML said it had 11 million active accounts, up 390 per cent, while its stored value balance lifted 170 per cent to $393 million.It's this number that will produce value over the short term, assuming its customers are inattentive."Accrued breakage," Cregan said, was $13.2 million, "and will convert to cash over the coming 12 months."Gross margins EML said improved by 1.5 percentage points to 78.4 per cent, and are "upwards of 90 per cent on some programs."