Only invoices bearing an electronic stamp from a PAC are legally valid for tax purposes, so your choice of an Authorized Certification Provider is a critical question that should be carefully analysed. Here we give you four mistakes you must not make when choosing your PAC:

First mistake: Not to demand an SLA that guarantees service availability

Can you imagine if you were unable to issue your invoices because your PAC’s stamping services had crashed? Your supplier should undertake to provide a minimum quality level through a SLA (Service Level Agreement), detailing their commitment to ensure availability of service 24 hours a day seven days a week.

Second mistake: Failing to check security in communications

A CFDI includes contact details, information on prices, discount, etc. The information contained in your invoices is sensitive and has to be transmitted over the network to be certified by the PAC. Make sure that your communications are reliable, and that your invoices not only reach the PAC, but also that they do so through secure channels that protect the confidentiality of your data.

Third mistake: No adding added value CFDI-issuing to your platform.

Practically all taxpayers in Mexico must issue CFDIs. So why does your purchasing department keep on receiving invoices on paper? Why should your sales Department keep printing out invoices? Why not improve your processes and save costs by including value-added options to your CFDI solution, such as electronic invoice deliveries or direct integration of accounts payable with your accounting system?

Fourth mistake: Delaying the decision to migrate to CFDI

If your annual turnover is more than $250,000.00 or you are issuing CFDs, you must migrate to the CFDI electronic billing scheme before 1 January 2014. It is not advisable to delay your decision to migrate to this new invoice issuing system. The sooner you take a decision, the more time you will have to carry out as many trials and checks as required.

Source: http://newsroom.edicomgroup.com/en/2013/09/23/mistakes-to-avoid-when-hiring-a-pac/