VAT adjustment report

I’ve encountered a difficulty while prototyping autoliquidation for construction project subcontracting in the French plan.

The problem is with credit notes which may or may not be booked in the same tax period(*) as the invoice (similar difficulty whether supplier or client invoice).

3310 CA3
Block A :
For autoliquidation, the declaration of the autoliquidation base is in line 02 (code 0981) for suppliers (subcontractor) invoices, and in line 05 (code 0033) for client invoices.
Block B:
suppliers autoliquidated invoices base and tax amounts in line 08(code 0207) and the deductable counterpart in line 20(code 0702)
nothing to do for client invoices

Normally, if the credit note is in the same tax period, the credit note would reverse these operations.
But when the credit note comes in a subsequent period one proceeds to a regularisation, lines
3C (code 0036) and 7B (code 0039) respectively in Block A, and potentially line 15 (code 600) and line 21 (code 0059 + special notice) for only supplier credit notes.

The problem is I don’t see any mechanism in the tax handling to deal differently the credit notes when in the same period or not.

(*) This is exacerbated with the typical case of cash-basis tax reporting.
That is, in France, it would probably be fair to consider practically all construction [sub]contractors are on a tax cash basis… which is, as mentioned previously in the lists, by default for services.
To add some hot oil to the problem, frequently, in many [larger] projects, the subcontractors are paid directly by the end customer (and not the prime contractor) making it a bit harder to control the precise amounts paid to the subcontractors, and when. It is even mandatory in public works projects for 1st level subcontracts depassing 500€ (read virtually all of them).

So how can one stipulate in tax_fr.xml that a autoliquidated supplier credit note needs simply to be deducted, for example, from line 02 if in the declared period but added to line 3C as a regularisation if posterior to the period where the credited invoice was declared to the tax authorities.


I guess we are missing the concept of adjustment on the tax line and on the tax code.
I do not think it is really possible to have it filled automatically because the definition of “adjustment” may vary by country. Also it is quite exceptional operation that requires anyway the intervention of an accountant.
So the accountant would have to edit the tax line on the generated move and activate the adjustment flag.
But we could eventually also add the flag on the invoice line and invoice tax.