Hello Rebecca Coker,
Generally we use General Journal to upload the YTD balances. You can use either open in excel or data management.
For open in excel; you can generate this from the general journal form itself, using General journal line entry entity. Once this is generated; you will find relevant columns where you can paste your data. You can further click on Design to add any other table. Once a new table is added, you have to update and refresh the open in excel. The table will be added as a new column. Once you fill all data in relevant columns, just Publish it back in D365.

If you are using Data management; then you can open the Data management workspace. Else, you will find this option in System administration module too. Once you open the Data management, you can export the template from the system itself by clicking on "Export". Once the template is ready with the data, click on "Import", select the "Source Data Format" which is excel; select the entity General journal; click on "Upload" tab to upload the template. Once done; you have to finally click on Import to upload the data in system.

You can find videos on YouTube to check each and every steps to follow.
Best regards,
Sourav Dam
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