{ "expense":
{
"user":"https://api.freeagent.com/v2/users/93049",
"category":"https://api.freeagent.com/v2/categories/249",
"dated_on":"2013-05-08",
"gross_value":"-100.0", # Note required if a mileage expense
"sales_tax_rate":"20.0",
"description":"TEST expense from API",