First of all: The contact

Whenever we register a supplier, we have to go to the accounting tab and select a "type of operation" (our customers' accountant should know this info!). Also, Odoo will automate the nationality if the supplier comes from a different country. in case it is not automated, we just select the nationality. It is not an obligation to have the Tax ID (RFC) but it would be nice to count with it.

This is how the contact form looks like: 

Whenever we make an operation with this supplier (including IVA) then it will appear like this on our report:

*The type of party field ("tipo de tercero") is automated by the natinality: 04 - national, 05 - foreign and 15 - global supplier (only god knows what a global supplier might mean)

Second ... Taxes:

The DIOT report is all about the "IVA Trasladado". It makes sense since all the Transferred VAT is money that you have the right to be refunded by the government (that's why SAT wants to know all the details related to transactions in which you paid this tax - justify this reimbursement). Therefore, other famous and beloved mexican taxes such as IEPS do not impact this report (so don't freak out if you can't see them on it). 

Given this context, the way in which we configure our taxes (related to IVA) is very important. Looking into the IVA(16%) Tax, a standard Odoo tax for purchases, we find this:

The distribution of the tax for invoices and credit notes have a "DIOT 16%" tag on the Base. What does this mean? That our report will be impacted on the IVA16% column with the untaxed amount of our vendor bill. For example, for this bill: 

The DIOT report will show this:

Note: This will only be posted on the report whenever the payment is made (if the invoice was paid partially, each of the payments will generate a line of report). This is the legal baseline in Mexico and all taxes should be configured this way! Also, if no invoice is attached to a payment, then no line is generated in the report. Actually, only when the payment is attached, the smart button for "asiento base de efectivo" will appear:

So, if a customer asks for a VAT retention, an Exempt VAT or even VAT that may not be creditable. Then we should configure this taxes (a later forum post will be made for the details of this), and assign the correct tax tag on the base. Example for a retention:

Note: This tags are already loaded with the MX_Loc module*

Finally, when all our taxes are configured and used in trasnactions, then we will see our DIOT report with the right amounts on the right columns :)