We are currently using Sage 50 to manage both SL and PL and therefore have no complications when it comes to VAT submissions through MTD.
It has been proposed that we will use a standalone billing/SL software to manage Invoices and receipts. The original proposal was that period totals from the billing software would be posted to Sage (single entries for each period) therefore the SL would be replicated within Sage and VAT submissions continue as normal.
On reflection, I don't believe this would meet requirements for a digital link as the period totals taken from a report and posted by hand into Sage seems open to error.
If the software produced a CSV which could then be uploaded in Sage 50 would this meet requirements. Additionally should that CSV contain line by line net and vat detail or could a total period value afor net and vat suffice because the detail is still a digital record albeit on another system to the system used for the digital submission.