This is possible, the companies need to be set up as a subsidiary.
This may have already been done, one way to check this:
Click Access Digital Tax and scroll down the page to your data sources,
Next to your data source, click the pencil icon and select your data source.
If your company has been set up as a subsidiary then you can select both companies for the data source and this means that both of those are covered under the one VAT return.
If this is not the case then please raise a new case online and reference the title of this article.