Connection error when submitting a tax return to HMRC

Article ID: 866
Last updated: 15 Jun, 2022

If you receive a connection error message when attempting to submit an online tax return, this means that your submission isn't getting through to the Gateway quickly enough and the Gateway has closed the internet connection to prevent it becoming blocked.

The likely causes of this error are listed below. Work through the following sections in sequence.

Is the service working?

Go to HMRC Status Page to check that the HMRC service isn't down. 

Has HMRC already received my submission but the response hasn't been collected?

  1. Open your return.
  2. Click on Check & Finish at the top of the screen.
  3. Click on File Online.
  4. Click on Resume on the left – you may need to scroll down the screen.
  5. If you don't have a Resume button, move to the next section.

Is the connection to the TaxCalc server working?

Exit and then restart TaxCalc. From the top menu bar, go to Help > Check for updates.

Success: 'Your software is up to date' or the update appears under notifications.

Run the update and then proceed to the next step.

Failure: 'Unable to retrieve product version/Couldn't resolve hostname/Null response'.

Check your proxy server:

  1. Open Internet Explorer (even if you use Firefox or Chrome daily).
  2. Go to Tools > Internet Options.
  3. Click on the Connections tab.
  4. Click on LAN settings.
  5. Check that Automatically detect settings is ticked.
  6. Check that Proxy server is unticked and greyed out – if it's ticked, remove it.
  7. Click on OK to save the change.

Please Note: If you are in an office environment you may need to speak to the IT department before trying to change the proxy settings.

Check for updates again after any changes. From the top menu bar, go to Help > Check for updates.

Success: 'Your software is up to date' or the update appears under notifications.

Run the update and attempt to open your return and file online.

Failure: 'Unable to retrieve product version/Couldn't resolve hostname/Null response'.

Turn off Onspeed (a download accelerator) if present and file online, or speak to your office IT department to resolve.

Your firewall can block a program's access to the internet. To file your return online, TaxCalc will need access. Read the Knowledge Base article for How do I configure my firewall software? to find out how to fix this.

Check Proxy Server Settings Dialog within TaxCalc

  • Go to Settings>Proxy Server Settings
  • Ensure that the option 'No Proxy' is selected as default *(Note that if a proxy setting is in place, either 'Use system proxy settings' or 'Manual proxy configuration' must be checked)
  • Click Update 

Is there a problem with my PDF attachment?

If the above steps don't work and you've attached a PDF to your return, that might be causing the problem. HMRC sometimes has problems with PDFs generated from a scanned paper document or files any bigger than 50KB. If you've created your PDF by scanning, follow these steps:

  1. If you have a soft copy (for example, a Word or Excel file), generate a PDF directly from that. 
  2. If you don't have a soft copy, rescan the paperwork using a lower resolution and in black and white/greyscale.

Please Note: If you don't have Adobe, you can use free software to convert a file to PDF – for example, pdf995 or CutePDF.

Attempted to hotspot to rule out internet issues? 

If the problem persists, it would be recommended to hotspot your phone to your machine and attempt the submission again. This will confirm whether it is your local internet service causing the issue. For assistance setting up the hotspot, use the following attached knowledge based article: Connecting to the internet through a mobile phone hotspot

If the submission is successful after using the hotspot, then you will need to contact your internet service provider to ensure that the following addresses are unblocked:


Still not working?

If you still can't submit your return, restart your computer (which should restart your internet connection). This will ensure that any outstanding Windows updates will be completed. If this doesn't work, contact our support team.

Article ID: 866
Last updated: 15 Jun, 2022
Revision: 14
Views: 11936
This article was:  

Also read
item Network Access is Disabled

Also listed in
folder Tax Return Production -> Filing Online
folder Technical
folder Technical -> Firewalls and Proxy Servers