MTD will apply to all VAT registered entities that are over the VAT threshold (£85,000) from April 2019. Any business and unincorporated entities over the VAT threshold to set up a digital tax account and file quarterly returns online.
Voluntary registered but under threshold are not required to follow MTD. However, they can elect to follow MTD. Threshold does not include outside of scope or exempt. Charities are not required.
You cannot leave unless you deregister for VAT. If you qualify for MTD for VAT you have to stay in unless you deregister. Even if your turnover drops below the threshold.
If a business deregistered from VAT it will not be required to store information in MTD compliant form.
The first return that will have to be MTD compliant will be the First VAT period on or after 1st April 2019.
Depending on your VAT Stagger (this is when your VAT returns are due) your first MTD return will vary.