An individual is permitted to make an application for a No Time Limit (NTL) to be endorsed on his/her passport as long as he/she has been granted Indefinite Leave to Remain (ILR) on an old passport. A new Indefinite Leave to Remain (ILR) will be issued to the person on a biometric residence permit normally called the BRP card.
Same day visa service is available for the NTL application giving you the opportunity to get a decision on the application within 24 hours.
Say for example you have lost or want to replace your Indefinite Leave to Remain application - whether old style or new style, you may need to make an NTL application on that basis.
When we say old style, we refer to the old way of endorsing or granting indefinite leave to remain. It used to be by way of a stamp on your passport or a letter saying that you have you have been granted indefinite leave to remain. New style on the other hand refer to where you have been granted indefinite leave to remain in a Biometric Residence Permit (BRP).
What we have seen is that some employers who do not know what the old style indefinite leave to remain looks like may be wary of your claim that you have indefinite leave to remain on the basis of that document.
The No Time Limit application therefore allows you to apply for a Biometric Residence Permit that most employers and the general public is more conversant with.
The No Time Limit therefore essentially just converts the Indefinite Leave to remain that you already have to a card.
In addition, if you are in a situation where your employer is not sure you have indefinite leave to remain and it is affecting your work, once you lodge an application you can ask your employer to contact the Home Office to verify that the application is in progress.
Once your employer have done this, they are covered with regards to liabilities and negligence. You are then able to continue working for them. Note that you never lost your right to work in the UK.