Applications for indefinite leave to remain (ILR) in the UK for Tier 1 General Visa holders must be submitted by 5 April, 2018 at the latest. Tier 1 General ILR closes on 6 April, 2018 and so this UK settlement route is being withdrawn from this date. You should make sure that you have passed the Life in the UK Test before you apply and in some circumstances you may need to pass an English language test.
The Tier 1 General Visa category was an enormously successful visa category when it was introduced by the Labour Government in 2008. However over the years anti-immigration sentiment has increased. These days for skilled workers from outside the EU the only UK visa route in many cases is the Tier 2 Visa route sponsored by an employer with a Tier 2 sponsorship license