---
title: "BuildsReferences – API-Referenz · Quittio"
description: "Document references (BT-10 to BT-19, BG-3) and the invoiced object."
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---

> Index of every page on this site: [llms.txt](https://quittio.dev/llms.txt)

[API reference](https://quittio.dev/docs/api) / [Quittio](https://quittio.dev/docs/api/Quittio) \\ [Core](https://quittio.dev/docs/api/Quittio/Core) \\ [Builder](https://quittio.dev/docs/api/Quittio/Core/Builder) \\ [Concerns](https://quittio.dev/docs/api/Quittio/Core/Builder/Concerns)

# BuildsReferences

trait in quittio/core

`Quittio\Core\Builder\Concerns\BuildsReferences` · [Source](https://github.com/Quittio/quittio/blob/v0.7.1/packages/core/src/Builder/Concerns/BuildsReferences.php#L21)

Document references (BT-10 to BT-19, BG-3) and the invoiced object.

Part of `InvoiceBuilder`, which holds the state; use the builder, not the trait.

## Methods \#

| Method | Description |
| --- | --- |
| `->buyerAccountingReference()` | The buyer's accounting reference (BT-19), e.g. a cost centre; null removes it. |
| `->buyerReference()` | Buyer reference (BT-10). For public sector buyers in Germany this is the Leitweg-ID. |
| `->contractReference()` | Contract reference (BT-12); null removes it. |
| `->despatchAdviceReference()` | Despatch advice reference (BT-16); null removes it. |
| `->invoicedObject()` | Identifier of the invoiced object (BT-18), e.g. a meter or subscription number, with its scheme (BT-18-1). |
| `->precedingInvoice()` | Adds a reference to a preceding invoice (BG-3): its number (BT-25) and issue date (BT-26), e.g. for a corrected invoice or a credit note. |
| `->projectReference()` | Project reference (BT-11) with the project name, which CII requires in addition to the identifier. |
| `->purchaseOrderReference()` | The buyer's purchase order reference (BT-13); null removes it. |
| `->receivingAdviceReference()` | Receiving advice reference (BT-15); null removes it. |
| `->salesOrderReference()` | The seller's sales order reference (BT-14); null removes it. |
| `->tenderReference()` | Tender or lot reference (BT-17); null removes it. |

### `buyerAccountingReference()`#

```
public function buyerAccountingReference(?string $reference): static
```

The buyer's accounting reference (BT-19), e.g. a cost centre; null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `buyerReference()`#

```
public function buyerReference(?string $reference): static
```

Buyer reference (BT-10). For public sector buyers in Germany this is the Leitweg-ID.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `contractReference()`#

```
public function contractReference(?string $reference): static
```

Contract reference (BT-12); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `despatchAdviceReference()`#

```
public function despatchAdviceReference(?string $reference): static
```

Despatch advice reference (BT-16); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `invoicedObject()`#

```
public function invoicedObject(string $value, string|RawCode|null $scheme = null): static
```

Identifier of the invoiced object (BT-18), e.g. a meter or subscription number, with its scheme (BT-18-1).

| Parameter | Type | Description |
| --- | --- | --- |
| `$value` | `string` | |
| `$scheme` | `string\| [RawCode](https://quittio.dev/docs/api/Quittio/Core/Codes/RawCode)\|null` = `null` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `precedingInvoice()`#

```
public function precedingInvoice(
    string $number,
    Date|DateTimeInterface|string|null $issueDate = null,
): static
```

Adds a reference to a preceding invoice (BG-3): its number (BT-25) and issue date (BT-26), e.g. for a corrected invoice or a credit note.

| Parameter | Type | Description |
| --- | --- | --- |
| `$number` | `string` | |
| `$issueDate` | `[Date](https://quittio.dev/docs/api/Quittio/Core/Support/Date)\|DateTimeInterface\|string\|null` = `null` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `projectReference()`#

```
public function projectReference(string $id, ?string $name = null): static
```

Project reference (BT-11) with the project name, which CII requires in addition to the identifier.

| Parameter | Type | Description |
| --- | --- | --- |
| `$id` | `string` | |
| `$name` | `?string` = `null` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `purchaseOrderReference()`#

```
public function purchaseOrderReference(?string $reference): static
```

The buyer's purchase order reference (BT-13); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `receivingAdviceReference()`#

```
public function receivingAdviceReference(?string $reference): static
```

Receiving advice reference (BT-15); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `salesOrderReference()`#

```
public function salesOrderReference(?string $reference): static
```

The seller's sales order reference (BT-14); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

### `tenderReference()`#

```
public function tenderReference(?string $reference): static
```

Tender or lot reference (BT-17); null removes it.

| Parameter | Type | Description |
| --- | --- | --- |
| `$reference` | `?string` | |

<dl><dt>Returns</dt>
<dd><code>static</code></dd>
</dl>

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```