REST API - Unable to specify VAT rate on client prepayments / credits

Extensibility
1

Hi,

I’m currently integrating with the v2 API and I believe there is a missing field on POST /client_payments when creating a client prepayment.

The endpoint supports creating a credit by specifying:

{
  "type": "credit",
  "date": "2026-10-02",
  "client_id": 123456,
  "amount": 1000.00,
  "currency": "GBP",
  "nominal_code": 1200,
  "notes": "Account credit"
}

According to the API documentation, type: "credit" is used for holding funds on a client’s account, which is exactly what we need.

However, there doesn’t appear to be any way to specify the VAT rate/treatment of that prepayment.

The problem

When we create prepayments through the API, they appear to be created with a 20% VAT rate by default.

For example, we may receive a £1,000 account top-up from a client whose eventual supply should not have 20% UK VAT applied.

We currently have to send:

POST /client_payments

{
  "type": "credit",
  "date": "2026-10-02",
  "client_id": 123456,
  "amount": 1000.00,
  "currency": "GBP",
  "nominal_code": 1200
}

The credit is successfully created, but we have no way through the API to tell QuickFile what VAT treatment should apply to the unallocated prepayment.

This is particularly important because QuickFile uses the VAT rate associated with an unallocated prepayment when calculating VAT returns.

The QuickFile web interface already allows the VAT rate to be selected when creating/assigning a prepayment, so there seems to be a difference between what can be done through the web interface and what can be done through API v2.

Expected behaviour

Ideally POST /client_payments would expose the same VAT options available when creating a prepayment through the QuickFile interface.

For example:

{
  "type": "credit",
  "date": "2026-10-02",
  "client_id": 123456,
  "amount": 1000.00,
  "currency": "GBP",
  "nominal_code": 1200,
  "vat_rate": 0
}

Obviously those field names are only examples, the main requirement is to be able to specify the same VAT treatment through the API that can already be selected when creating the prepayment manually.

Could you confirm whether there is currently an undocumented parameter for specifying the VAT rate/treatment on a client credit?

If not, could this be added to POST /client_payments so that API-created prepayments have feature parity with prepayments created through the QuickFile interface?

Thanks,
Lewis

2

Hi @TheNeco

This isn’t supported at present, but we can certainly look at adding it in the future.

The initial aim with the new API is to ensure we mirror the functionality available on the legacy API. We can then look to building on top of that to add features such as the one you’re querying.

Although the VAT rate is 20%, if it’s later assigned to an invoice with a different rate, this will be adjusted accordingly, assuming you’re on cash accounting for VAT.