A company that I did some work for and I earned more than 600$ is asking me to fill out a w9 for 2017 in order to receive a 1099 ( the request to fill out the w9 has been made after January 31 2018 which is the deadline to receive a 1099)
I already filed taxes for 2017 and I reported the income as 1099 misc.
The company never asked a w9 when I started the contract work.
Do i have to fill out that form or can i ignore it ?
That is up to you. As long as the income is reported, you've done your part as the IRS is looking for all income. The 1099 that you should have received is also reported to the IRS, so reporting it was the right thing to do. If you get a 1099 later, no need to do an amendment. You've already reported the amount and if needed, you can explain that later should the IRS try to adjust based on the 1099 they receive. Here's more on 1099's: