5.1. Straight Line Method

In the straight line method, we assume that the depreciation rate is uniform over its useful life, meaning that every year the machine loses the same value. This method calculates depreciation as:

$D = \frac{IC - S - TC}{n}$

Where:

• $IC$: Initial Cost
• $S$: Salvage Value
• $TC$: Tire Cost
• $n$: Useful Life in years

The straight line method of depreciation is an accounting technique used to allocate the cost of an asset over its useful life evenly. In simple terms, this means if you buy a machine, you divide its cost evenly over the number of years you expect to use it. Every year, the same amount is deducted as depreciation from the machine's value, which reflects its decreasing worth over time. The formula provided helps in calculating the specific annual depreciation value by considering how much the machine was bought for (initial cost), how much it will be sold for at the end (salvage value), and any additional costs associated (like tire costs).

Imagine you buy a new smartphone for $800, and you expect to use it for 5 years. You also realize that the phone case, which costs$50, won't last as long. So, you only consider the phone's cost minus the expected $50 from its value when it is sold at the end of its life. Each year, you would account for losing$150 in value (i.e., $800 initial cost -$50 salvage value divided by 5 years = $150 per year) as it gets older, which helps you understand how much it's worth each year.

It’s important to note that the tire cost depreciates at a different rate than the rest of the equipment. Therefore, tire costs should be deducted from the initial cost when calculating the depreciation.

$D = \frac{IC - S - TC}{n}$

Where $TC$ is the tire cost that must be excluded from the initial cost.

In many machines, tires do not last as long as the machine itself. This means they depreciate faster than the overall equipment. As such, when calculating straight line depreciation, the cost of the tires should be removed from the initial cost, so you're only calculating depreciation on the part of the equipment that matches its useful life. This refinement provides a more accurate depreciation estimate.

Think about a car, where the frame and engine last for many years, but the tires need regular replacement every few years due to wear. If you wanted to know how much value the car lost annually, you'd factor in that the tires lose value quicker than the vehicle as a whole. By focusing solely on the car's structure for depreciation while accounting separately for tires, you get a clearer picture of the car's overall financial depreciation.

The straight line method is straightforward and easy to apply. However, it is not commonly adopted because it provides lower depreciation values for newer machines. Many companies prefer methods that accelerate depreciation to show higher expense in early years for tax benefits.

While the straight line method simplifies depreciation with equal annual deductions, it doesn't reflect reality where some assets lose value faster at the beginning of their lives. In practical terms, businesses may prefer to use accelerated depreciation methods even though the straight line is simpler because it can help them write off costs more quickly, which can lower their tax obligations during those early years.

Consider a laptop that you buy for your business. If you use the straight line method, you'd show the same loss in value each year, $200 if counted over five years. However, in reality, the first year might see you lose more value due to technology advancements. Therefore, using a faster depreciation method could more accurately reflect the laptop's declining value and help with taxes if you account for higher expenses during that time.

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