You will need to bring your current passport and any immigration documents from the Home Office and United Kingdom Visa and Immigration (UKVI). This may include your 30 day entry clearance vignette, your Biometric Residence Permit card, and any other documentation that UKVI have issued to you.
We also recommend that you bring your boarding passes and flight details with you to the RTS Check. If they are needed, the IST staff member will tell you.
If you have made a visa application from within the UK but have not received a decision, bring a printed version of the application form with you. If you forget to do this, the RTS Check will not be completed.