# Customizing Tryton?

**URL:** https://discuss.tryton.org/t/customizing-tryton/5152
**Category:** User
**Created:** [March 31, 2022, 9:42pm UTC](https://discuss.tryton.org/t/customizing-tryton/5152 "2022-03-31T21:42:04Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![pokoli](https://discuss-cdn.tryton.org/user_avatar/discuss.tryton.org/pokoli/32/22_2.png) [@pokoli](https://discuss.tryton.org/u/pokoli)
#### Post date: [April 1, 2022, 8:49am UTC](https://discuss.tryton.org/t/customizing-tryton/5152/2 "2022-04-01T08:49:10Z")

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> [@Toni](#):
>
> Q1: I would like to have customer-specific numbers. So far, I understand that a “Party” is a customer if I create a sales invoice to them. I found an old thread about adding customer specific fields, like their EU VAT-Id etc., and I would need a text field for the customer, too. Is modifying the ‘Party’ model still the way to go, or could it work in a different way?

It’s hard to say without knowing more about the number usage.  
But if it is just for searching and identifing a party I will add them as Identifiers of the party as this fields are using when searching parties.

> [@Toni](#):
>
> so that the next invoice will have an invoice number of, say, ‘ABC000124’.

It is strange to have specific sequence for customer. Probably what you are requesting is what we already discussed [on this post.](https://discuss.tryton.org/t/allow-different-invoice-sequences-on-the-same-period/1779)

> [@Toni](#):
>
> Irrespective of when I create an invoice, I would like to have it being issued on the next business day. I would also like the payment terms to be calculated on the invoice date. Lastly, I would like those invoices be emailed on the date specified on the invoice

I think you will need to code here. The best is to have a cron job that post customer invoices with a date today. You can use [notification\_email](https://docs.tryton.org/projects/modules-notification-email/en/latest/) module to automatically email the invoices when post.

> [@Toni](#):
>
> In Germany, we need to declare VAT electronically, and I would like to have this process automated.

If this is something generic to the whole country I think the best is to extend the german localization modules to include the process to generate the required file format or to talk with the webservice. We’ve done that in the Spanish localization and it works very well as all the features all available for all german customers.

> [@Toni](#):
>
> Are these still recommended, or what should I be looking at, short of sifting through the entire source code?

There is a [Work in Progress to include a developer tutorial](https://codereview.tryton.org/32711002/) in the oficial documentation, you may be interested in having a look at it as its quite advanced.  
Lets see if we can make it ready for the upcoming release.

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