When migrating to a new EHR you will need to split your 835 files (aka. Electronic Remittance Advice files) so you can post payments to the appropriate system (i.e., your legacy system and your new system). This can be done by splitting the 835 files by claim identifier or service date. Forefront has software to split by these and other fields. Refer to this article Splitting an 835 file or contact us at info@ForefrontTechnologiesOnline.com for more information.