If you work with the IMSS Sistema Único de Autodeterminación (SUA) and encounter the message “Error al calcular cuotas bimestrales” (Error calculating bimonthly contributions), this article will guide you step by step to resolve the issue. This error is one of the most common when generating the contribution determination and can be caused by corrupt data in the database, an outdated SUA version, or incorrect dates in the Salary Base of Contribution (SBC) integration.

The Error

When attempting to generate the bimonthly contribution calculation from the Determinación de cuotas > Cálculo menu, SUA displays the message:

“Error al calcular cuotas bimestrales”

In some cases, the error is accompanied by a numeric code or an additional message such as “No se pudieron procesar los registros del período seleccionado” (Could not process records for the selected period). The calculation screen may close abruptly or simply fail to generate the expected determination file.

The error typically appears in the following scenarios:

  • When calculating the bimonthly period for the first time after entering affiliation movements
  • After updating the SUA version without restarting the computer
  • When trying to recalculate a bimonthly period that already had a previous determination with modified data
  • When handling a large number of workers (more than 500 records)

Root Cause

The bimonthly contribution calculation error in SUA has several possible root causes:

1. Corrupt worker data

The SUA database (SUA.MDB file) stores all worker information in Microsoft Access format. Over time, records can become corrupted due to power outages, abrupt program closures, or hard drive failures. When SUA tries to read a corrupt record during calculation, the process fails.

2. Outdated SUA version

IMSS periodically publishes SUA updates that include calculation formula corrections, adjustments for contribution rate changes, and security patches. If your version is not current, the calculation engine may fail when encountering scenarios not covered by the older version.

3. Incorrect SBC dates

Each worker’s Salary Base of Contribution (SBC) must have a valid integration date that corresponds to the bimonthly period being calculated. If the integration date is after the end of the bimonthly period or before its start, SUA cannot correctly determine the contributions.

4. Inconsistent affiliation movements

Duplicate registration, salary modification, or termination movements within the same period generate conflicts in the calculation. SUA requires a clean, sequential history of movements for each worker.

5. Fragmented database

After multiple registration, termination, and modification operations, the database can become fragmented. Even though the data may be valid, fragmentation causes read errors during intensive operations like the bimonthly calculation.

Step-by-Step Solution

Step 1: Identify workers with errors

  1. Open SUA
  2. Go to Determinación de cuotas > Cálculo
  3. Select the bimonthly period and year you want to calculate
  4. Click Calcular
  5. When the error appears, review the error report that is generated
  6. Note the social security numbers (NSS) of workers appearing in the report
  7. If the error doesn’t generate a report, select Reportes > Errores de cálculo to review it

Step 2: Verify worker data

For each worker identified with an error:

  1. Go to Afiliación > Consulta/Modificación de trabajadores
  2. Search for the worker by NSS or RFC
  3. Verify the following fields:
    • Full name: no special characters or extra spaces
    • CURP: 18 characters, valid format
    • Worker type: permanent or temporary as applicable
    • Salary type: fixed, variable, or mixed
    • SBC (Salary Base of Contribution): correct amount according to the current salary integration
    • Start date: must be prior to the beginning of the bimonthly period
  4. Correct any incorrect data and save the changes

Step 3: Correct affiliation movements

  1. Go to Afiliación > Movimientos afiliatorios
  2. Select the worker by NSS
  3. Verify that a registration movement (type 08) exists with a date prior to the bimonthly period
  4. If there are salary modifications (type 07), verify that dates are sequential and don’t overlap
  5. If you find duplicate movements, delete the duplicate by selecting it and clicking Eliminar
  6. If necessary movements are missing, enter them with the correct dates

Step 4: Update SUA to the latest version

  1. Visit the IMSS portal at idse.imss.gob.mx
  2. Navigate to the SUA downloads section
  3. Download the installer for the latest available version
  4. Close SUA completely (verify it’s not in the taskbar)
  5. Run the installer and select the Update option
  6. Do not uninstall the previous version, as this would delete the database
  7. Restart the computer once the installation is complete

Step 5: Repair the database

If the error persists, the database may be damaged:

  1. Close SUA completely
  2. Navigate to *C:\CobranzaSUA* in File Explorer
  3. Locate the SUA.MDB file
  4. Make a backup copy of this file to another location (desktop or USB)
  5. Open the SUA.MDB file with Microsoft Access
  6. Go to Tools > Database Utilities > Compact and Repair Database
  7. Wait for the process to finish (may take several minutes depending on size)
  8. Close Access and open SUA again

Step 6: Recalculate bimonthly contributions

  1. Open SUA
  2. Go to Determinación de cuotas > Cálculo
  3. Select the correct bimonthly period and year
  4. Click Calcular
  5. Verify the report shows no errors
  6. If the calculation was successful, go to Determinación de cuotas > Disco de pago to generate the payment file

Alternative Solution

If the steps above don’t resolve the problem, you can try the following alternatives:

Reinstall SUA with backup import

  1. Generate a full backup from Utilerías > Respaldo de información
  2. Save the backup to a safe location (USB or desktop folder)
  3. Uninstall SUA from Control Panel > Programs and Features
  4. Manually delete the *C:\CobranzaSUA* folder if it remains
  5. Download and install the latest SUA version from the IMSS portal
  6. Once installed, go to Utilerías > Restaurar información and import your backup
  7. Try the bimonthly contribution calculation again

Manually calculate problematic workers

If only a few workers cause the error:

  1. Identify the problematic NSS numbers
  2. Delete the bimonthly period movements for those workers
  3. Re-enter them manually with the correct data
  4. Run the calculation again

Use the data verification tool

  1. Go to Utilerías > Verificación de datos
  2. Select Verificar todos los registros
  3. SUA will display a report of inconsistencies found
  4. Correct each inconsistency before recalculating

Prevention

To avoid this error in the future, follow these recommendations:

  • Update SUA regularly: check monthly for new versions on the IMSS portal
  • Back up the database before each bimonthly calculation using Utilerías > Respaldo de información
  • Verify movements before calculating: use Reportes > Movimientos afiliatorios to confirm everything is in order
  • Compact the database at least once per bimonthly period using Microsoft Access
  • Close SUA properly: never shut down the computer with the program open
  • Install SUA on a dedicated computer: avoid shared computers where other programs may interfere with SUA files
  • Check current rates: make sure your SUA version reflects the current fiscal year contribution rates, especially after reforms to the Social Security Law
IssueProbable causeQuick fix
”No workers found for the period”Registration dates outside the bimonthly periodCheck start dates in Afiliación
”SBC out of range”Integrated salary exceeds contribution capAdjust SBC to the current 25 UMA cap
”SIPARE payment file error”Incorrect determination file formatRecalculate and regenerate the file
”Duplicate movement”Repeated registration or modification for the same NSSDelete duplicate in Movimientos afiliatorios
”Damaged database”Corruption of the SUA.MDB fileCompact and repair with Access or reinstall SUA

Summary

  • The bimonthly contribution calculation error in SUA is mainly caused by corrupt data, outdated versions, or incorrect SBC dates
  • Identify workers with errors by reviewing the calculation error report
  • Verify and correct each worker’s data: SBC, start dates, and affiliation movements
  • Update SUA to the latest version available from the IMSS portal
  • Repair the SUA.MDB database with Microsoft Access if corruption is present
  • Always back up the database before performing bulk operations
  • Compact the database regularly to prevent fragmentation