Once you have qualified for the physical presence or bonafide resident tests ( form 2555), then the first year's ( the partial year) exclusion max will be an allocated amount based the number of days abroad. You can now ( if you are abroad, then it is June 15th ) either file a normal return including the foreign income and then when qualified file an amended return OR get an extension and file a proper return ( i.e. with foreign earned income exclusion in effect ) when you qualify.
