Using the Rupee Sign
The Indian rupee sign combines the Devanagari letter र (ra) with a Latin R missing its stem, crossed by two parallel lines that stand for the tricolour flag and the equals sign. The design by D. Udaya Kumar won a public competition and was adopted by the Government of India on 15 July 2010; Unicode added it as U+20B9 in version 6.0 a few months later. It is one of the youngest currency signs in wide use, which explains almost every problem people have with it.
Why it shows as a box on some devices
A font can only draw characters that existed when it was made. Phones, printers, e-readers and embedded systems built before roughly 2011 ship fonts that stop at the older generic ₨, so ₹ appears as an empty rectangle or a question mark. Windows 7 needed an update to gain it, and some point-of-sale systems and SMS gateways never got one. The fix is not on your side: if the audience might be on old hardware, write Rs 499 or the ISO code INR 499, both of which are plain ASCII and cannot fail.
Placement and the lakh grouping
The sign goes before the number without a space: ₹250, ₹1,999.50. Indian figures group digits by twos above the thousands, so one hundred thousand is ₹1,00,000 and ten million is ₹1,00,00,000, read as one lakh and one crore. International reports use the Western grouping ₹100,000 instead; pick the convention your readers know and keep it consistent through the document. Paise take two decimal places, though most retail prices now round to whole rupees.
₹ versus ₨ and Rs
The older ₨ at U+20A8 is a single character that looks like the letters Rs pressed together. It is still the correct sign for rupees outside India, including Pakistan, Sri Lanka, Nepal and Mauritius, and it is what you will find on Indian documents printed before 2010. Using it for Indian rupees today is not wrong, just dated. The typed abbreviation Rs, with or without a full stop, remains common in headlines and in text messages.
Typing it
Windows includes the sign on the English (India) keyboard layout under Ctrl + Alt + 4, and in Word you can type 20B9 followed by Alt + X on any layout. Macs have no default shortcut, so the Character Viewer or a text replacement is the practical route. On iPhone, adding the English (India) keyboard puts ₹ on the number layout where $ normally sits, and Gboard on Android shows it in the long-press menu on the dollar key.
In Instagram and YouTube bios the sign flags Indian pricing for commissions and courses, and it sits comfortably next to the euro sign or pound sign in a multi-currency price list. Decorative alphabets from the fancy fonts generator rarely include a stylised ₹, so keep it in plain text between the styled words.