The Singapore visa application for an Indian citizen requires an NOC certificate. I currently work in a start up and there is no official letterhead. A travel agency that I contacted told me that the letterhead is mandatory. How should I go about this?
Startups are famously flexible in the way things are done, which in your case is a good thing. It will only take twenty minutes for someone in your HR Department to prepare a letterhead for your purpose.
Note that in Singapore, it is mandatory to mention the company registration number (UEN No.) on invoices and letterheads and other official stationery of the Company, if any.
A sample of a NOC can be found here
Make sure you get the authority of someone in responsible for HR/Administration to sign off on the paperwork.