Not sure how true, but found on CTR forum, quoting directly below. I guess it's better to take these steps to prevent the expensive titanium exhaust from becoming a worthless item once LTA fails it - unless you're sure the welded section is so tiny and inconspicuous that they wouldn't notice it.
"Hey I just did this last month.
OFFICIALLY, you are supposed to:
1) Make an appointment with an LTA officer to inspect and take photos of your damaged area BEFORE you weld (usually at the VIACOM inspection centre nearest to LTA HQ)
2) Weld the exhaust and obtain tax invoice for your welding (not sure if welding die die has to be done at the authorized distributor of your exhaust or not)
3) Make another appointment with LTA officer to inspect and take photos of the repaired area after the weld. You'll need to submit the tax invoice from the workshop to the LTA officer as well.
The photos and record of your exhaust "mod" will henceforth be stored in LTA's record for your name/car - for reference during future inspections.
The above is what I have been adviced and gone through. Any bro is welcome to share any faster procedure you may have experienced otherwise.
Felt kinda silly to go through all these just to repair a few cracks in my exhaust"
"Welding need not be done in front of LTA officer, though a friend (don't ask me how he did it) once managed to get the LTA officer to come down to view the welding at the workshop (to the shock of everyone at the workshop LOL) - saving a lot of time in the process (basically steps 1-3 all done at once).
Note that I didn't have to pay any inspection fee at Viacom, as the inspection pit was booked directly by the LTA officer and the inspection was carried out by the same officer (no Viacom staff was involved)."