Registered LLC in Los Angeles, California - a software development agency w/o physical office. Should I obtain LA Tax Registration Certificate and what it imposes?

[satspace]

In 2017 I registered LLC in California. It is a software development agency. I have no physical office and no employees in LA. My home address is my LLC mailing/legal address, which is in Los Angeles. Recently I received a letter from City Of Los Angeles says that I should apply for "City of Los Angeles Business Tax Registration Certificate". It is not clear if software development agency as sole proprietary LLC should obtain LA Business Tax Registration Certificate. 

Question: Can anyone explain why is it needed, what does it impose, will I pay extra tax to LA, if yes - how much?. Should I register at all if in 1 month I will be closing my LLC in California?

I couldn't find any software development category when tried to apply for LA Business Tax Registration Certificate online. I tried to read through finance.lacity.org FAQ - but is not informative. 

[TomD8]

"Any individual or entity conducting business activities within the City of Los Angeles is required to apply for and obtain a Business Tax Registration Certificate with the City of Los Angeles, Office of Finance."   http://finance.lacity.org/registering-your-business

Doesn't say anything about a requirement to have a physical office or employees.

However, you may want to read about the Small Business Exemption: http://finance.lacity.org/tax-incentiveexemption