The Puerto Rico Treasury Department has published Circular Letter No. 19-10 of 4 April 2019 concerning quarterly returns for withholding at source (10%) on services rendered using a new quarterly return form, Form 480.6 SP-1. In general, the return is to be filed by the end of the month following each quarter, although the Circular Letter provides that for the first quarter of 2019 ending 31 March, the deadline is 31 July (i.e., the returns for both the first and second quarter are due 31 Ju…