I need to be added to the Zivilstandsregister (Zurich City) for Citizenship.

I contacted the Zivilstandsregister and they said "fill in a form and we will then write back asking for further documents from your home country"

I filled in the form and sent it off, unfortunately it is taking a while for them to reply.

Can I ask what documents they will ask for, so that I can prepare in advance?

I am not married and have no children.

Birth certificate (less than 6 months old)

In your case bachelorhood certificate (less than 6 months old)

If not in German/French/Italian/English then translated by an appropriate translator (with a copy of their ID)

Depending on the combination of your country of birth / citizenship you may or may not need to get these document apostilled.

If your county of birth issues an international format birth certificate no need for apostille.

If your country of citizenship has signed the European Convention on the Abolition of Legalisation of Documents executed by Diplomatic Agents or Consular Officers then any documents issued by your embassy or consulate in Switzerland suffice as is and need not an apostille.

thanks, I am British. I don't think there is a "bachelorhood certificate" in Britain.

Also this the British Embassy has a document you can print out that there is no central civil status registry in Britain.

However if you are getting married there is: Certificate of No Impediment

I think I will need to call the Embassy unless anyone has an input?

If it is not possible to provide a document from your home country that proves your bachelorhood then they'll ask you to submit a notarized sworn statement that you have never been married.
For some reason they first wanted me to get such a statement notarized at my country's Swiss consulate but in the end they accepted one notarized at a random notary public in Zurich when I suggested to them that the consul of my home country had exactly the same amount of knowledge that I was not lying as a Swiss notary public (i.e. zero).

I sent my application in Q3 last year and definitely did not have to provide this Bachelorhood certificate... I have never even heard of such a thing.

Maybe because you are married (or divorced) and your civil status is already in the Zivilstandsregister.

This thread is not about a naturalization application but registering at the Zivilstandsregister prior to submitting it. In OP's case this is as an unmarried person (hence the bachelorhood certificate) not born in Switzerland meaning they would not show up in the federal Zivilstandsregister beforehand.

I have just done this also for citizenship and as you are not married the only thing that you need is a birth certificate. In Romania we have now what is called Multilingual Extract of your birth certificate. Google says UK has one...You do not have to notarize it as it is accepted as an official copy but not more than 6 months old. A friend of mind from Hungary got his from his embassy in Bern. As UK is not EU it might not be accepted anymore.