Personal Tax/VAT- Invocation of the constructor ‘CefSharp WPF Chromium Web browser’ etc.

personal-tax-vat-invocation-of-the-constructor-cefsharp-wpf-chromium-web-browser-etc

Personal Tax/VAT- Invocation of the constructor ‘CefSharp WPF Chromium Web browser’ etc.

28th May 2026

You get this error when using PT MTD, PT Data retrieval, VAT filer.

There is a possible local IT issue on your PC/SERVER/HOST SITE which is blocking a HMRC login screen from showing on your Browser and you get errors like below: Without this HMRC login screen – you cannot sign in and get the PT/VAT from working.

a) VAT obligations will not appear for a client

b) PT data retrieval will not work for a client

c) PT MTD Quarters do not appear for a client

As this could be environment related on your pc/server/host, so ask your IT team to review these areas.

1. Review your anti virus and local security setups. Also if you have an antivirus set up or similar – you can test this by switching it off and then try and use PT/VAT. If it then works you may have found the cause.
2. Check your IT setup is allowing Chrome and Edge to be run. This is because it requires the browsers edge/chrome to be setup correctly/fixed or the connection with HMRC will fail and you get that error.
3. One user reported back to us they had to get Edge/Chrome ‘to be added to exclusion’ which then stopped the warnings and allowing VAT/PT users to work again.