---
title: "+=(_:_:)"
framework: foundation
role: symbol
role_heading: Operator
path: "foundation/decimal/+=(_:_:)"
---

# +=(_:_:)

Adds two decimal numbers, storing the result in the first number.

## Declaration

```swift
static func += (lhs: inout Decimal, rhs: Decimal)
```

## Parameters

- `lhs`: A value to add.
- `rhs`: Anothervalue to add.

## Discussion

Discussion If the result of this operation requires more precision than the Decimal type can provide, the result is rounded using the NSDecimalNumber.RoundingMode.plain rounding mode. To specify a different rounding mode, use the NSDecimalAdd(_:_:_:_:) function instead.