"From 1 April 2019 all VAT registered businesses with a taxable turnover above the VAT threshold (£85,000) are required to keep their VAT business records digitally and send their VAT returns using MTD-compatible software."
The fundamental change mandated by Making Tax Digital is that filing your VAT return will not be possible using the HMRC online portal (the website) from 1st April 2019. Instead you will have to submit the VAT Return data through the HMRC API. This can only be done using software approved by HMRC. A list of approved vendors, including Bridge Squared, is available from HMRC - Software suppliers supporting Making Tax Digital for VAT.
Though this is a subtle change from the current mechanism, there are significant ramifications which should not be ignored. The use of a direct connection from your business records system / accounts package through to HMRC should reduce the risk of declaration errors through mis-typing.
The key consequence of this legislation is that mandated businesses must keep digital business records from 1st April 2019.