Absolutely. It's not a problem at all to join Songtrust if you are affiliated to the PRS and/or MCPS. Once you have signed up with us, we will ensure that PRSforMusic will be notified of our agreement to administer your publishing.
Joining Songtrust for your publishing administration will not affect your writer royalties which will continue to flow to you directly from the PRS. Moving forward, unless you choose for us to administer your publishing excluding the UK/Eire territory, you will no longer need to inform the PRS directly about your new copyrights. You can simply upload the new songs to your Songtrust account, and we'll do the rest!