Hi, 

When manually entering a supplier invoice with multiple tax lines, the invoice will look similar to the following. Tax line 1 amount 100 tax code A, Tax line 2 amount 200 tax code B.  Total invoice 300.  The posting lines will look like the following posting line 1 for tax code line A 60, posting line 2 tax code line A 40, and then posting line 1 for the tax code B line 200.    In other words, the posting lies are connected to the lines produced by the tax codes. Most importantly, the posting amounts, must match the data (values) on the tax lines.  100 must match the 60 /.40.   The 200 must match postings that total 200. 

Assuming you're loading a text or CSV file for the external invoice the file must include similar data structure.   The tax codes will be in the tax lines section, and then your posting lines must then also be connected to those tax lines.   Based on the error message, it looks like your postings per tax line do not match the tax lines.    In using the above example my external invoice file would have 2 tax lines 1 and 2, and 3 posting lines. Posting line 1 and 2 would link to the tax line 1, and posting line 3 is connected with tax line 2. 

Based on the error message your file does not comply with the above. 

I can’t find a good example of a file with multiple tax. Check your posting lines and make sure they tie correctly to the various tax lines.  

Best regards, 

Thomas