This error arises if your internet settings are set to a security protocol that is no longer supported by HMRC.
This can be fixed by changing your internet settings, so long as you are using Windows 7 or later.
Please note that Windows 7 or later is required to submit MTD VAT returns to HMRC. If you get this error and are using a version of Windows older than Windows 7, you will not be able to submit returns and will need to use a more recent version of Windows.
To set the correct protocols:
1.Open the Control Panel in Windows (To find the control panel on your version of Windows please click here.)
2.Select Network and Internet (skip this step if you are using Windows 10)
3.Select Internet Options and then the Advanced tab
4.Make sure the following settings are unticked or ticked accordingly:
a)Use SSL 3.0 is unticked
b)Use TLS 1.0 is unticked
c)Use TLS 1.1 and Use TLS 1.2 are ticked
5.Click on Apply
6.Submit your MTD VAT return again in the usual way