SAT, RFC, CFDI, tax regime and e.firma can feel like an impossible alphabet. The order matters more than the vocabulary. SAT wants your business to register correctly, invoice what it sells and file the returns that match the operation.
Use each answer as a verification path
For any SAT question, record the RFC, tax period, obligation and source consulted before acting. If one of those elements changes, the answer may also change. This small habit keeps a general explanation from being applied to the wrong taxpayer or period.
This guide is for you if you are starting, already selling but not invoicing, or invoicing without a clear monthly process.
Quick Answer
Start with the basics: active RFC, correct tax regime, updated tax status certificate, valid e.firma, working SAT password, correct customer tax data, CFDI process and a monthly review of invoices against bank records and returns.
If only three things get done this week, make them these: download your tax status certificate, validate your SAT access and reconcile your latest invoice against the bank deposit.
RFC in Plain English
The RFC is your Mexican taxpayer ID. Without it, you cannot issue valid invoices, file returns or complete many business procedures.
- Individual taxpayer: usually the business and the person are the same taxpayer.
- Legal entity: the company is a separate taxpayer and may be necessary when there are partners, employees or growth plans.
- The right choice depends on activity, revenue, risk, partners and future operations.
Do not choose only by intuition. Review current income, projected growth and obligations before registering or changing regime.
E.firma and SAT Password
The e.firma is your electronic signature for SAT procedures. It is used for filings, invoices, Tax Mailbox and online procedures. The SAT password is useful too, but it does not replace every e.firma use.
Keep files and passwords protected. If several people need access, define who can do what and how activity is documented.
CFDI 4.0: The Invoice Basics
A CFDI is the official electronic invoice. It is not a Word receipt or a nice PDF. It has a valid XML that supports income and expenses before SAT.
Before issuing, request:
- Customer RFC.
- Tax regime.
- Fiscal postal code.
- Correct CFDI use.
- Product or service code.
- Payment method and form consistent with the real collection.
If one of these fields is wrong, the invoice may be rejected, canceled or useless for deduction.
Minimum Tax Compliance Habit
You do not need an expensive system to start. You need a reliable monthly habit:
- Issue CFDI when you sell.
- Save XML and PDF for every invoice.
- File monthly returns on time.
- Review whether annual return applies.
- Reconcile income, expenses, bank records and returns.
- Monitor the Tax Mailbox.
When to Stop Doing It Alone
Ask for help when invoices, deposits and returns no longer match, when a SAT notice arrives, when you have employees, partners or more than one income source, or when you do not understand which regime applies.
A good accountant does more than file returns. They help read the operation before a small difference becomes a larger problem.
Quick Checklist
- RFC active and activity updated.
- E.firma valid and stored securely.
- SAT password working.
- Tax status certificate updated.
- Correct customer tax data.
- Clear CFDI 4.0 issuing process.
- Monthly invoice, bank and return reconciliation.
- Filing calendar.
- Tax Mailbox enabled.
- Accountant or advisor ready when questions grow.
How Fintax Can Help
Fintax helps organize the first layer of compliance: RFC, CFDI, returns, Tax Mailbox and evidence. The goal is to move from scattered doubts to a process your business can repeat every month.
Official links to complete the task
Open official services from a new browser tab, confirm the taxpayer and period, and save the resulting acknowledgment or evidence with the case.
