> For the complete documentation index, see [llms.txt](https://docs.fieldmotion.com/fieldmotion-api-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fieldmotion.com/fieldmotion-api-docs/invoice/_setdiscounttax.md).

# \_setDiscountTax

Sets the Tax value in an Invoice

### Parameters

#### id

The ID of the Invoice being modified

#### val

The amount of Tax set for the Invoice, 1 is considered a euro (e.g 2.49 => €2.49)

### Example

```
FM_api('Invoice_setDiscountTax',[
  'id'=>'697943',
  'val'=>'2'
]);
```

### Result

#### On Success

```
{"ok":1}
```

#### On Failure

If the "id" parameter is missing or has a value less than 1:

```
{"error":"missing or invalid parameter: id"}
```

If the "val" parameter is missing:

```
{"error":"missing or invalid parameter: val"}
```

If the Invoice being modified has its Status set as Paid:

```
{"error":"cannot edit invoices that are marked Paid"}
```

If the "val" parameter value contains non-numeric characters (e.g a-z):

```
{"error":"invalid discount tax"}
```