If I upload a 1099 for a joint account, but file separately, do I need to enter the full amounts, or only the portion I earned?

You can enter the amounts that you earned if the 1099 is issued to both joint account holders.  Generally, if you receive a Form 1099 for amounts that actually belong to another person, you are considered a nominee recipient. You must file a Form 1099 with the IRS (the same type of Form 1099 you received) for each of the other owners showing the amounts allocable to each.