"I need the rest to adjust."
No, you absolutely don't.

Yes, every record should have a unique value but the actual value you use should not matter a fig!
It doesn't matter that they're not in order or, at least, it shouldn't matter. Certainly, your database won't care.

What if you have another file, somewhere else, that also has these values in it, but with (say) millions of rows. Are you seriously going to go through all of those and change them all instead of just inserting one new "record" with the next available number?
It's a huge performance hit (potentially millions of rows being updated instead of just one) and a massive risk of data corruption (what if those identifiers somehow "come to rest" linked to the wrong person ("my" transactions suddenly become "yours")?

Regards, Phill W.