When filing tax, Year of Assessment (YOA) refers to the year you are reporting income for — not necessarily the year you are filing.

Simple Rule

Year of Assessment = Previous year’s income

Example

If you are filing in 2026:

You are reporting income earned in 2025

So your Year of Assessment = 2025

More Examples

When You File

Income Year

Year of Assessment

2026

2025 income

2025

2025

2024 income

2024

2024

2023 income

2023

Nigeria Tax Rule (Important)

In Nigeria:

Tax returns are usually filed between January 1 — March 31

And it’s for the previous year’s income

So right now (2026):

You should normally use 2025 as your Year of Assessment

Special Cases

However, it can differ slightly if:

You’re filing for backlog years

You’re filing first time

You’re filing for company vs individual