Updater fails with Unexpected Error SerializationException. Both for the main program and when trying to install the State program.

I was able to solve it with the following that was found in another answer:

1. Close TurboTax and then click here to download and install SQL Server Compact 4.0 from Microsoft's website.
2. Open Windows Explorer and browse to the location C:\Program Data\Intuit\Common\Update Service\v4\Global.
3. Right-click the Global.sdf file and choose Properties.
4. Click the Security tab.
5. In the Group or user names area, select your username and click the Edit button.
6. In the new window, select the Allow checkbox that corresponds to Full Control, and then click OK twice to close the windows.
7. Try updating TurboTax again.

HI, i found clearing out the directory where i was installing the forms etc helped me. If you re-install you may try to remove all files or use a new directory during the install. I also downloaded a copy of turbotax instead of using my dvd rom disk. It ran much faster. Not sure this will help in your situation but it's something to try.

Which file should be downloaded?? I see two choices: 1 is 

and the other is 

Depends on your computer.  Most likely the x64 version, unless you have an old 32-bit computer, then use the x86.

Yep, I did the 64 and got it to work. Thanks.

1) Close TurboTax

2) Go to Task Manager, click on the "Services" tab. Try finding "IntuitUpdateServiceV4".

3) Right click on the service and click on "Stop" to stop the updater service.

4) Once the updater service is stopped, Go to "C:\ProgramData\Intuit" path and delete the "Common" folder.

5) After deletion, restart the Updater service i.e. Go to Task Manager, click on the "Services" tab. Try finding "IntuitUpdateServiceV4" ,right click on the service and then click on "Start" option.

6) Once the Updater service is started, try opening TurboTax again.

Hello.  I tried below, but get a message that the "Global" is corrupted/unreadable when I click on the folder.  Any ideas?

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I was hours on the phone with tech support, and they couldn't help me.  Thank you.  This worked. 

I tried 5 other fixes. This one worked ! 

The SQL Server Compact Download 4.0 link is no longer available. I manually updated my Federal Turbo Tax but I CANNOT download my State!

May I ask what state you are attempting to download @HelpMare? Are you receiving a specific error?

I get Unexpected Error

System.Runtime.Serialization.SerializationException: Type is not resolved for member ...

EVERY TIME I go into Turbo Tax, when I try to update it AND when I try to download North Carolina state software.

I just tried KenLam's fix from above and that worked without downloading the SQL. I was able to download North Carolina State software.

It would be best to contact us by phone by following the instructions here so we can look into this further @HelpMare. 

Thank you for the post. I was unable to update TurboTax 2021 due to the same error. I was able to solve the problem as you noted. I used KenLam's fix from above and that worked without downloading the SQL.

@cjk005 So glad you were able to get the software downloaded. Thanks for updating us!