Form CT-603 when applying for Tier-2 sposnorship

My employer is at the final stages before applying for a Tier-2 sponsorship, as part of my immigration process.

it seems that we have all the documents, except CT-603, which is a notice for sending in a complete tax return (CT-600).

Since it's a notice document, my employer didn't keep this document. is there any alternative document we can supplement?

Please help!