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Dynamics 365 Community / Forums / Small and medium business | Business Central, N... / Solution for Duplicate...
Small and medium business | Business Central, N...
Suggested Answer

Solution for Duplicate values in External Document Number in Business Central.

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Posted on by SS-22091817-0 12

Hello Everyone,

 

I would like to clarify if in the External Document Number field, where we capture Purchase Order (PO) numbers, can it Allow Duplicates.

Since the same PO number may be referenced across multiple transactions, it is important that this field supports duplicate entries.

If not, what are the other solutions to this problem?

Thank you for help.

 

Categories:
Dynamics 365 Business Central
I have the same question (0)
  • Suggested answer
    Valentin Castravet Profile Picture
    Valentin Castravet 32,319 Super User 2026 Season 1 on at
    The External Document No. (Vendor Invoice No.) must be unique. When you post, the system checks for duplicates and blocks an existing number. If you need to reuse it, change it slightly, for example: if the original no. is1000, you can change it to 1000., 1000v1, or 1000v2. The exact pattern is up to your business.
     
  • Suggested answer
    Suresh Kulla Profile Picture
    Suresh Kulla 50,269 Super User 2026 Season 1 on at
    Firstly, the Ext. Doc No. Mandatory setting on Purchases and Payables setup is designed to prevent duplicates and ensure that a user cannot post an order without an Ext. Document No. Disabling this setting can solve the issue. 
    But if you don't enforce this requirement the user can post without a external doc. no. To enforce and have duplicates you need to do a customization.
  • Suggested answer
    Pallavi Phade Profile Picture
    Pallavi Phade 5,424 Super User 2026 Season 1 on at
     
    Below Setup in Purchase & Payables , Ensure below things
    1) External document no should not be blank
    2) External document no should not be duplicate 
     
     
    But if we need to allow Duplicates then
    1) we need to remove boolean from above setup
    2) Create our customization
    2.1 Not to allow blank External Document Number
    2.2 Allow Duplicate External Document Number based on business logic if any
     
    Write Customization in below event - 
     
     
    IF you feel this helped , please mark as "Verified" 
     
    Regards
    Pallavi Phade
  • Suggested answer
    Nimsara Jayathilaka. Profile Picture
    Nimsara Jayathilaka. 4,950 Super User 2026 Season 1 on at
    Hi
     
     
    In Business Central, the External Document No. field is normally set to be unique per vendor to help prevent duplicate invoices being posted by mistake. By default, the system will give you a warning or error if you try to reuse the same number on another purchase invoice for the same vendor.
     
    But the answer is Yes, Business Central can allow duplicates, but you’ll need to either adjust the setup or use an alternative field depending on whether you want duplicate checking switched off system-wide or only for certain cases.
  • Suggested answer
    Valentin Castravet Profile Picture
    Valentin Castravet 32,319 Super User 2026 Season 1 on at
    Just FIY the Ext. Doc. No. Mandatory field in Purchases & Payables Setup only controls whether Vendor Invoice No. is required when posting. It does not control if the value in this field can be a duplicate.
     
  • Suggested answer
    YUN ZHU Profile Picture
    YUN ZHU 99,322 Super User 2026 Season 1 on at
    Hi, I mentioned in the following post, hope the it can give you some hints.
    Dynamics 365 Business Central: Set External Document No./Vendor Invoice No. as mandatory (Ext. Doc. No. Mandatory)
     
    Thanks.
    ZHU
  • Suggested answer
    Rishabh Kanaskar Profile Picture
    Rishabh Kanaskar 6,219 Super User 2026 Season 1 on at
    Hi,
     
    By default, Business Central checks for duplicate External Document Numbers per vendor and prevents posting duplicates to avoid accidental double-posting.
     
    If you need duplicates:
    > Go to Purchases & Payables Setup, enable Ext. Doc. No. Mandatory and turn on Allow Document No. Duplication.
    > This allows the same PO number across multiple transactions.
     
    Alternative: use a custom field to store reference numbers if you want duplicates without changing standard behavior.
     
    Thanks
    Rishabh
  • Suggested answer
    Valentin Castravet Profile Picture
    Valentin Castravet 32,319 Super User 2026 Season 1 on at
    There’s no ‘Allow Document No. Duplication’ field on Purchases & Payables Setup, so that advice is incorrect.
     

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