diff --git a/api/tax_calculator/controllers.py b/api/tax_calculator/controllers.py
index 15d667b..0e4ad93 100644
--- a/api/tax_calculator/controllers.py
+++ b/api/tax_calculator/controllers.py
@@ -7,14 +7,32 @@ def get_reliable_brackets():
     return get_tax_brackets()
 
 
-def get_unreliable_brackets(tax_year):
-    naptime()
+def calculate_tax(salary, tax_year):
+    brackets = get_tax_brackets(str(tax_year))
+    total_tax = 0
+    tax_bands = []
 
-    # be evil
-    roulette = random.randint(1, 4)
-    print(f'Database roulette {roulette}')
-    if roulette == 3:
-        raise Exception("Database not found!")
+    for bracket in brackets:
+        min_income = bracket['min']
+        max_income = bracket.get('max', None)
+        rate = bracket['rate']
 
-    return get_tax_brackets(tax_year)
-    
\ No newline at end of file
+        if max_income is not None and salary > max_income:
+            tax_amount = (max_income - min_income) * rate
+        else:
+            tax_amount = (salary - min_income) * rate
+
+        total_tax += tax_amount
+        tax_bands.append({
+            'min_income': min_income,
+            'max_income': max_income,
+            'tax_rate': rate,
+            'tax_amount': tax_amount
+        })
+
+        if max_income is not None and salary > max_income:
+            break
+
+    effective_rate = total_tax / salary * 100 if salary > 0 else 0
+
+    return total_tax, tax_bands, effective_rate
diff --git a/api/tax_calculator/routes.py b/api/tax_calculator/routes.py
index b6259bb..d5f4692 100644
--- a/api/tax_calculator/routes.py
+++ b/api/tax_calculator/routes.py
@@ -1,10 +1,16 @@
-from flask import jsonify, render_template, redirect
+import logging
+
+from flask import jsonify, redirect, request
 from app import app
-from . import controllers
+from . import controllers, error_handlers
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
 
 
 @app.route('/tax-calculator/')
 def tax_calculator_instructions():
+    """Provide instructions for tax calculator API."""
     return jsonify({
         'tax_brackets': controllers.get_reliable_brackets()
     })
@@ -12,11 +18,63 @@ def tax_calculator_instructions():
 
 @app.route('/tax-calculator/tax-year')
 def default_brackets():
+    """Redirect to default brackets."""
     return redirect('/')
 
 
-@app.route('/tax-calculator/tax-year/<tax_year>')
-def tax_year_brackets(tax_year):
-    return jsonify({
-        'tax_brackets': controllers.get_unreliable_brackets(tax_year)
-    })
+@app.route('/tax-calculator', methods=['GET'])
+def tax_calculator():
+    """
+    Calculate total tax based on salary and tax year.
+
+    Returns:
+        jsonify: JSON response containing total_tax, tax_bands, and effective_rate.
+    """
+    try:
+        salary = float(request.args.get('salary'))
+        tax_year = int(request.args.get('tax_year'))
+
+        if tax_year not in [2019, 2020, 2021, 2022]:
+            error_message = 'Invalid tax year. Only years 2019, 2020, 2021, and 2022 are supported.'
+            logger.error(error_message)
+            return jsonify({
+                'errors': error_handlers.format_error(
+                    error_message,
+                    field='tax_year'
+                )
+            }), 400
+
+        if salary <= 0:
+            error_message = 'Salary must be a positive value.'
+            logger.error(error_message)
+            return jsonify({
+                'errors': error_handlers.format_error(
+                    error_message,
+                    field='salary'
+                )
+            }), 400
+
+        total_tax, tax_bands, effective_rate = controllers.calculate_tax(salary, tax_year)
+
+        return jsonify({
+            'total_tax': total_tax,
+            'tax_bands': tax_bands,
+            'effective_rate': effective_rate
+        }), 200
+
+    except ValueError:
+        error_message = 'Invalid input types. Salary and tax_year must be numeric values.'
+        logger.error(error_message)
+        return jsonify({
+            'errors': error_handlers.format_error(
+                error_message,
+            )
+        }), 400
+    except Exception as e:
+        error_message = str(e)
+        logger.error(error_message)
+        return jsonify({
+            'errors': error_handlers.format_error(
+                error_message,
+            )
+        }), 500
diff --git a/api/tax_calculator/test_tax_calculator_api.py b/api/tax_calculator/test_tax_calculator_api.py
index 2373980..53bc9da 100644
--- a/api/tax_calculator/test_tax_calculator_api.py
+++ b/api/tax_calculator/test_tax_calculator_api.py
@@ -1,10 +1,20 @@
 import os
 import json
 
+
 brackets_dir = os.path.join(os.path.dirname(__file__), 'fixtures')
 
+
 def _get_brackets(tax_year):
-  
+    """
+    Get tax brackets for a specific year.
+
+    Parameters:
+        tax_year (str): The tax year for which to retrieve the brackets.
+
+    Returns:
+        dict: A dictionary containing the tax brackets for the specified year.
+    """
     filename = f'tax-brackets--{tax_year}.json'
     file_with_path = os.path.join(brackets_dir, filename)
 
@@ -15,7 +25,140 @@ def _get_brackets(tax_year):
     return json_contents
 
 
-def test_basic_route(client): 
-  resp = client.get('/tax-calculator/')
-  brackets = _get_brackets('2022')
-  assert resp.json == {'tax_brackets': brackets}
+def test_basic_route(client):
+    """
+    Test the basic route for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/')
+    brackets = _get_brackets('2022')
+    assert resp.json == {'tax_brackets': brackets}
+
+
+def test_valid_input(client):
+    """
+    Test valid input for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?salary=100000&tax_year=2021')
+    assert resp.status_code == 200
+    data = resp.json
+    assert 'total_tax' in data
+    assert 'tax_bands' in data
+    assert 'effective_rate' in data
+
+
+def test_invalid_tax_year(client):
+    """
+    Test invalid tax year input for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?salary=100000&tax_year=2018')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert error['field'] == 'tax_year'
+    assert 'Invalid tax year' in error['message']
+
+
+def test_negative_salary(client):
+    """
+    Test negative salary input for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?salary=-10000&tax_year=2022')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert error['field'] == 'salary'
+    assert 'positive value' in error['message']
+
+
+def test_invalid_input_types(client):
+    """
+    Test invalid input types for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?salary=abc&tax_year=2022')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert 'Invalid input types' in error['message']
+
+
+def test_no_params(client):
+    """
+    Test no parameters provided for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert error['message'] == 'Both salary and tax_year parameters are required.'
+
+
+def test_missing_salary(client):
+    """
+    Test missing salary parameter for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?tax_year=2022')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert error['field'] == 'salary'
+    assert 'required' in error['message']
+
+
+def test_missing_tax_year(client):
+    """
+    Test missing tax year parameter for the tax calculator API.
+
+    Parameters:
+        client: The Flask test client.
+
+    Returns:
+        None
+    """
+    resp = client.get('/tax-calculator/?salary=50000')
+    assert resp.status_code == 400
+    error = resp.json['errors'][0]
+    assert error['code'] == ''
+    assert error['field'] == 'tax_year'
+    assert 'required' in error