TL;DR — Quick Summary
Fix CFDI rejected for incorrect IVA or ISR withholding: correct rates, tax base, Retenciones node and recipient regime before stamping in Aspel or PAC.
When stamping a CFDI with IVA and ISR withholdings, PAC or pre-validation may reject the receipt with incorrect withholding, invalid rate or withholding amount out of range. The error usually originates in the Retenciones XML node, where SAT-required exact rates must appear based on service type and issuer/recipient tax regime.
This guide explains frequent causes in Mexico, correct ISR and IVA withholding calculation, and the procedure to stamp without rejections in Aspel SAE, CONTPAQi or other billing systems.
The Error
Typical messages when stamping with misconfigured withholdings:
CFDI40108: Withholding amount is not valid
CFDI40161: Withholding rate or quota is not valid
Withheld amount doesn’t match tax base
Retenciones node error: unrecognized tax
IVA withholding must be two-thirds of transferred IVA
Stamping stops, no UUID is generated and the transaction lacks fiscal proof.
Root Cause
CFDI 4.0 withholdings must follow specific SAT rules per transaction scenario. Approximate percentages aren’t enough — base, rate and rounding must be exact.
Wrong ISR rate for service type
ISR withholding varies by scenario:
| Scenario | ISR rate | Notes |
|---|---|---|
| Professional fees (individual) | 10% | On subtotal without IVA |
| Lease (individual lessor) | 10% | On rent without IVA |
| Commercial commissions | 2% | On commission amount |
| Goods transport services | 4% | Individuals |
Applying 10% when 2% applies, or withholding ISR on total including IVA, causes rejection or declaration differences.
Mis-calculated IVA withholding
When the recipient must withhold IVA (e.g. fees to individuals), the rate is 10.6667% — two-thirds of 16% IVA on the tax base.
Common errors:
- Withholding full 16% instead of 10.6667%.
- Calculating on subtotal + IVA instead of transferred IVA.
- Rounding to 10.67% without six decimals in TasaOCuota.
Correct formula for professional fees:
IVA base = Subtotal × 16%
IVA withholding = IVA base × (2/3) = Subtotal × 10.6667%
ISR withholding = Subtotal × 10%Wrong tax base
ISR is withheld on subtotal without IVA. IVA withheld is calculated on transferred IVA. Mixing bases invalidates the Retenciones node.
Missing or malformed Retenciones node
If withholding is required but XML lacks Retenciones with taxes 001 (ISR) and 002 (IVA), PAC may reject. Each withholding needs:
- Impuesto: 001 or 002
- Importe: amount with two decimals
- TasaOCuota: rate with up to six decimals (e.g. 0.100000 for 10% ISR)
Incompatible issuer tax regime
Legal entities receiving services from individuals with withholding must issue CFDI where the recipient withholds. Wrong PF regime or recipient not marked as withholding obligor in ERP causes missing or wrong default rates.
Inconsistent rounding
SAT validates Importe = Base × TasaOCuota with minimal tolerance. Rounding each line separately can cause cent differences PAC rejects.
Step-by-Step Solution
Step 1: Identify withholding scenario
- Confirm service type: fees, lease, commissions, etc.
- Verify issuer RFC and tax regime (individual or entity).
- Confirm recipient (your company) must withhold per scenario.
Step 2: Calculate correct amounts
Example professional fees — subtotal $10,000:
| Concept | Calculation | Amount |
|---|---|---|
| Subtotal | — | $10,000.00 |
| IVA 16% | 10,000 × 0.16 | $1,600.00 |
| ISR withholding 10% | 10,000 × 0.10 | $1,000.00 |
| IVA withholding 10.6667% | 10,000 × 0.106667 | $1,066.67 |
| Total to pay | 10,000 + 1,600 − 1,000 − 1,066.67 | $9,533.33 |
Step 3: Configure in Aspel SAE
- Catalog > Vendors — confirm regime and withholding requirement.
- Catalog > Concepts — assign ISR and IVA withholding rates to fee concepts.
- When capturing vendor invoice, enable Retenciones in preview.
- Verify both nodes appear before stamping.
Step 4: Validate XML before stamping
Check preview for Retenciones with Impuesto 001 and 002, and TasaOCuota as 0.100000 and 0.106667.
Step 5: Stamp and record accounting
- Stamp CFDI and save XML + PDF.
- Deliver withholding certificate to vendor.
- Record withholdings for monthly SAT declarations.
Alternative Solution
Manual PAC portal: enter subtotal, IVA, withholdings with exact rates and stamp. Import XML to ERP if supported.
Prevention
- Keep concept templates with preconfigured withholding rates by service type.
- Train accounts payable on transferred vs withheld IVA difference.
- Update SAT catalogs and billing system version each fiscal year.
- Let ERP calculate with six decimals; don’t round manually.
Related Issues
CFDI without required withholdings: vendor may reject payment; cancel and reissue with correct withholdings.
Withholdings on credit notes: partial cancellation must adjust ISR and IVA withholdings proportionally.
Error 401 when stamping: renew CSD before fixing withholdings.
Summary
- Incorrect withholding usually stems from wrong rate, tax base or malformed Retenciones node.
- Typical fees: ISR 10% on subtotal and IVA 10.6667% (two-thirds of IVA).
- Configure rates in concept catalog and validate XML before stamping.
- Record withholdings for monthly SAT declarations.