Announcing IP Space with BGP and ASN Number

Currently my IP space is announced by my old upstream and there ASN. We now have another upstream we are doing BGP into. Can I simply start announcing my IP space on this new circuit with my ASN then a bit later have the old upstream cease announcing my IP space with there ASN?

Will there be any harm having two different ASN’s announcing the same space for a short period? It will certainly make the cut over easier. I can route all the incoming traffic from both into my network easily for the short transition and send all out bound too one or other.

That will not be a problem. BGP explicitly allows for this.

And it did work without any issues.