Failing to file 83(b) election

I worked for a start up for a year and I had 1/4 of my stock options vested. I decided to exercise the options and purchased it on 8/15. I gave them the check but it was not until last week (10/12) that I received the stock certificate/paper (or whatever it is called) stating that I own the stocks. On the paper, the date is 8/15.

1. Is it too late for me to file for 83(b) election?
2. To avoid disastrous tax consequences from increase in company's valuation, what options do I have?

My reference: http://www.accountalent.com/?p=429

Is it too late for me to file for 83(b) election?

Yes. You should have filed it when you received the restricted stock, not when it vests. Once it vests, you own it, and the gain is capital gain anyway, you're taxed on the value at vest as ordinary income.

To avoid disastrous tax consequences from increase in company's
valuation, what options do I have?

Now? Nothing in particular. 83(b) should be filed within a month from the grant date, which has long passed.

From your link:

• If you have stock options, you do not need to file an 83(b) Election
Form.

• If you purchased/received founder’s stock and there are no
restrictions, such as vesting, you do not need to file an 83(b)
Election Form.

• If you purchased/received restricted stock in a
growing startup, you should probably (about 99% of the time) file an
83(b) Election Form.

Keep in mind that I'm not a licensed tax adviser or professional. When in doubt - talk to a EA/CPA licensed in your state. Do not rely on anonymous free information on open internet forums, it is worth exactly what you paid for it.