I went through a similar experience recently where I had to upgrade my normal application process to tatkaal due to business travel urgency. This upgrade is only possible after your police verification has been done and you are in urgent need to expedite the remaining formalities. Overall process is summarized below:
1. After applying through Passport Seva Kendra, get your police verification done as soon as possible from local Thana and ensure that a clear report has been submitted from Police Commissioner Office to Regional Passport Office.
2. Following that you need to personally meet the Assistant Passport Officer at RPO with your urgency proof (can be an authorized letter from your company HR describing the urgency). Also don’t forget to carry your company id card. Even though I carried my id card, I had to visit RPO twice as my access card didn’t had a company logo on it and was explicitly asked to get a separate letter of affiliation on the following day.
3. Once the Assistant Passport Officer is convinced, you will be asked to get your urgency documents scanned into the system and pay a penalty of Rs.2000/- at specific counters.
4. After that you will be asked to meet the officer once again for some final remark/signature on the application token (issued while entering RPO).
5. And now, last but not least, expect your passport to be dispatched on the next working day.
Hope this should help others seeking to convert/upgrade their passport application from normal to tatkaal.