"Las obligaciones que este nuevo Régimen Fiscal nos pide: Llevar de manera electrónica un registro de todas sus operaciones de ingresos y egresos; tener documentación comprobatoria de cada operación, acto o actividad; enviar informe contable mensual a través de la página del SAT; expedir Comprobante Fiscal Digital por Internet (CFDI)."
http://www.elsiglodedurango.com.mx/noticia/535395.con-el-nuevo-regimen-fiscal-la-iglesia-catolica-pagara-impuestos-.html
Roughly traslated: The requirements of the new Fiscal System require: To record electronically a ledge of all income and expenses; to record and document all operations, acts or activities, to send a registed monthly report through SAT's (kind of like the IRS in the US) website, submit Comprobante Fiscal Digidtal por Internet (CFDI) (sort of tax form)
I just saw this today, I'll look more into it but it looks like the Mexican government is asking all religious and non-profit groups to submit all their financial data to avoid and detect money laundering-that's what the government is claiming the reason for this new tax reform.
There is some information I found that required these groups to pay taxes, I'm not sure about that yet but it looks like they may pay taxes and some Catholic priests say they already pay taxes. So I don't know, but this means that WT will have to be transparent in their financials if they want to give Ceasar what he's asking for.