The Mexican Tax Administration (SAT) decided to postpone again the date to implement the Complemento de Pagos (Supplement of Payments). Apparently, the new postponement is caused by the new technical difficulties in the integration of the new Complemento de Pagos with other aspects of the CFDI and the Contabilidad Electronica. This new Complemento was previously scheduled to take effect on April 1, 2018. At this point, the new effective date for the mandatory use of the Complemento de Pagos will be September 1, 2018.
The announcement of the postponement by the SAT is also contained in Third (Tercero) paragraph of the Anticipated Version of First Resolution of Modifications to the Miscellaneous Resolution for 2018, which is found at: http://www.sat.gob.mx/informacion_fiscal/normatividad/Paginas/RMF_2018_versiones_anticipadas.aspx