TL;DR — Quick Summary

IMSS SUA won't open SUA.MDB due to corruption. Repair with Jet Compact, restore backup, exclude antivirus, and avoid running from network shares.

Diagram

The message “The SUA file cannot be opened”, “Not a valid database”, or “Error opening SUA.MDB” blocks access to the IMSS Sistema Único de Autodeterminación (SUA). Without the database, the employer cannot capture affiliation movements, calculate quotas, or generate the SIPARE payment file for social security. Unlike NSS or outdated table errors, this means SUA.MDB in C:\CobranzaSUA\ is damaged, locked, or incomplete.

In many payroll offices the problem appears Monday morning after a power outage, Windows update, or manual copy of the database from another branch without properly closing SUA. Corruption may be total (program will not start) or partial (opens but fails on quota calculation or import).

The Error

When starting SUA or opening the database from utilities, Windows may show:

“Cannot open database ‘C:\CobranzaSUA\SUA.MDB’”

“The SUA file cannot be opened”

“Not a valid Microsoft Access database file”

“Error 3343: Unrecognized database format”

“Database is locked by another user”

If CobranzaSUA.ldb exists and nobody has SUA open, the lock is usually residual. If .ldb keeps reappearing, another PC on the network is using the same database — a scenario that also corrupts files.

Cause of the Problem

SUA.MDB is a Microsoft Jet/Access database the IMSS did not design for multi-user network use or careless virtualized environments. Most frequent corruption causes:

Abrupt shutdown or power loss

Powering off while SUA calculates quotas, imports a large .txt, or generates reports interrupts writes to internal tables. Jet leaves the database inconsistent.

Running from a network drive

Opening SUA.MDB on \\server\share\CobranzaSUA\ is a classic corruption cause. Two users — or the same user in different RDP sessions — write simultaneously and damage the file within days or weeks.

Antivirus and hot backup

Security software scanning every .mdb change can lock the file at the critical save moment. Backups copying SUA.MDB while SUA is open produce truncated, unusable copies.

Full disk or bad sectors

If drive C: fills during bimonthly calculation, Jet cannot complete the transaction. Bad sectors on old HDDs also trigger error 3343 or generic invalid file messages.

Incorrect manual copy

Copying only SUA.MDB without auxiliary tables, or pasting a database from another employer registration over the local folder, breaks references. Pasting an older base over the current one without backup deletes recent movements even if the file “opens.”

Incompatible SUA version

Mixing a base generated with a different SUA version than installed occasionally prevents opening until installer and IMSS tables align.

Step-by-Step Solution

1. Close SUA and back up entire CobranzaSUA

Open Task Manager and end SUA.exe and related processes. Copy the full folder:

C:\CobranzaSUA\

including SUA.MDB, table files, .ldb if present, and subfolders. Name the backup with date: CobranzaSUA_backup_2026-06-03. Never work on the only copy without a backup.

2. Remove .ldb lock

After confirming nobody uses SUA, delete CobranzaSUA.ldb. Try opening again. If the error persists, corruption is structural, not just a lock.

3. Compact and repair the database

Options depending on your environment:

  1. Microsoft Access: File > Info > Compact & Repair Database (on a file copy).
  2. Jet Compact command-line utility pointing to SUA.MDB.
  3. From SUA itself if it partially starts: maintenance menu when the IMSS installer includes it.

Save the result as SUA_reparado.mdb. Open SUA pointing temporarily to the repaired copy or rename after validating worker and movement queries.

4. Restore known good backup

If Compact fails or repaired data shows inconsistencies (zero quotas, duplicate workers):

  1. Restore the last good SUA.MDB backup before the failure.
  2. Note the backup date.
  3. Download IDSE .txt receipts for movements sent after that date.
  4. Re-import via Utilities > Import affiliation movements and Import IDSE response.

Reconcile active workers against payroll before recalculating quotas.

5. Reinstall SUA and register components

If the error mentions missing DLLs or OCX in addition to the database, reinstall SUA from the official IMSS package as administrator. Register components like threed32.ocx if needed. Install on local disk, not network.

6. Validate full operation

After recovery:

  1. Query a random worker under Affiliation.
  2. Run bimonthly movement report.
  3. Calculate quotas and generate test SIPARE (do not pay until amounts match payroll).

Prevention

  • Local install: one C:\CobranzaSUA\ folder per PC; sync only via scheduled backups, not concurrent use.
  • Daily backups: copy SUA.MDB at end of day with SUA fully closed.
  • Antivirus exclusion: add C:\CobranzaSUA\ to real-time scan exclusions.
  • UPS: avoid power loss during bimonthly close.
  • Disk space: keep at least 5 GB free on C: before quota calculation.
  • Branch copy procedure: export/import movements via IDSE instead of hot-copying .mdb.

Summary

  • “SUA file cannot be opened” usually means corrupt, locked, or incorrectly copied SUA.MDB.
  • Back up, remove orphan .ldb, run Compact/Repair, and if that fails restore backup + re-import IDSE.
  • Do not run SUA or open the database from a network share; exclude the folder from antivirus.
  • After recovery, validate movements, quotas, and SIPARE before bimonthly close.