The mandatory registration threshold is 375,000 AED. It means that when your local UAE turnover reaches this number or you expect it to be reached in the nearest month, you should register for VAT.
Voluntary registration threshold is 187,500 AED. Voluntary registration is done by the businesses who are planning to claim back VAT which they paid for their corporate expenses, for example office fitout and furnishings.
VAT de-registration should be done in 2 cases:
If you closed the company, you should apply for VAT de-registration right away to avoid penalties for late de-registration.
In case your business model has changed and you are not supposed to pay VAT in UAE, it is better to take a qualified advice and then apply for de-registration. The process may take a few months since Federal Tax Authority will need to check if your business is really no longer VAT liable.
In UAE VAT registration number is not assigned to the business at the time formation.
Every company liable for VAT must apply for registration through Federal Tax Authority portal. Registration is usually approved within a couple of weeks. Once its approved, your unique VAT registration number will be generated and assigned to your business.