Are you required to invalidate your previous citizenship?

[MrBrilliant]

Suppose you get your British Citizenship. What is your status afterward? Are you required to inform your previous country of origin that you are now a British Citizen? Do you have to invalidate your previous citizenship? Or do you become a dual citizen?

[vinny]

Dual citizenship (also known as dual nationality) is allowed in the UK.

[noajthan]

Gov UK position on dual citizens is here:
Dual citizenship

- but be careful about this:
Crackdown on criminals who change their names to avoid detection

> not sure how many criminals it's catching but it's proving tricky for some law-abiding married women;
(those who naturalise in UK in their married name but who hold official documents in their previous, maiden name)

[secret.simon]

As Vinny mentioned above, the UK allows multiple citizenship.

But the other country of which you are a citizen may not allow multiple citizenship.

Neither India nor Japan allow multiple citizenship and you lose their citizenship when you become a British citizen.

Other countries (for example, Austria and I believe South Africa) allow multiple citizenship if you ask for permission from their government before you apply for British citizenship.

Yet other countries (US, Canada, Pakistan, Ireland, etc) allow multiple citizenship as a matter of course.

It would be best to notify your other country of your becoming a British citizen. Indeed, it may be a criminal offence in that country if you don't.

Also, due to the Master Nationality rule, you can not claim British consular assistance when you are in any other country of which you are also a citizen.

To reiterate, none of this has anything to do with UK law. It is the law of the other countries of which you are a citizen that decides the requirements.