Payment Application Generator
Business Case
Problem Statement
Payment applications are error-prone:
- Manual calculations cause mistakes
- Retention tracking is complex
- Inconsistent documentation
- Delayed submissions affect cash flow
Solution
Automated payment application generation with schedule of values tracking, retention calculations, and standard format output.
Business Value
- Accuracy - Eliminate calculation errors
- Speed - Faster billing cycle
- Cash flow - Timely payments
- Compliance - Standard documentation
Technical Implementation
import pandas as pd
from datetime import datetime, date
from typing import Dict, Any, List, Optional
from dataclasses import dataclass, field
from enum import Enum
class SOVStatus(Enum):
"""Schedule of Values item status."""
NOT_STARTED = "not_started"
IN_PROGRESS = "in_progress"
COMPLETE = "complete"
STORED_MATERIAL = "stored_material"
@dataclass
class SOVItem:
"""Schedule of Values line item."""
item_number: str
description: str
scheduled_value: float
work_completed_previous: float
work_completed_current: float
materials_stored_previous: float
materials_stored_current: float
total_completed_previous: float
@property
def total_completed_current(self) -> float:
"""Total completed and stored this period."""
return (self.work_completed_previous + self.work_completed_current +
self.materials_stored_previous + self.materials_stored_current)
@property
def percent_complete(self) -> float:
"""Percent of scheduled value complete."""
if self.scheduled_value == 0:
return 0
return (self.total_completed_current / self.scheduled_value) * 100
@property
def balance_to_finish(self) -> float:
"""Remaining value."""
return self.scheduled_value - self.total_completed_current
@dataclass
class PaymentApplication:
"""Payment application (AIA G702/G703 style)."""
application_number: int
period_from: date
period_to: date
project_name: str
contractor: str
owner: str
contract_sum: float
change_orders_amount: float
retainage_percent: float
items: List[SOVItem] = field(default_factory=list)
approved_date: Optional[date] = None
approved_by: str = ""
@property
def total_contract_sum(self) -> float:
"""Original contract plus approved changes."""
return self.contract_sum + self.change_orders_amount
@property
def total_completed_this_period(self) -> float:
"""Work completed this billing period."""
return sum(item.work_completed_current + item.materials_stored_current
for item in self.items)
@property
def total_completed_to_date(self) -> float:
"""Total completed and stored to date."""
return sum(item.total_completed_current for item in self.items)
@property
def retainage_amount(self) -> float:
"""Total retainage held."""
return self.total_completed_to_date * self.retainage_percent
@property
def total_earned_less_retainage(self) -> float:
"""Amount earned less retainage."""
return self.total_completed_to_date - self.retainage_amount
@property
def balance_to_finish(self) -> float:
"""Remaining contract balance."""
return self.total_contract_sum - self.total_completed_to_date
class PaymentApplicationGenerator:
"""Generate and manage payment applications."""
DEFAULT_RETAINAGE = 0.10
def __init__(self, project_name: str, contractor: str, owner: str,
original_contract: float, retainage: float = None):
self.project_name = project_name
self.contractor = contractor
self.owner = owner
self.original_contract = original_contract
self.retainage_percent = retainage or self.DEFAULT_RETAINAGE
self.sov_items: Dict[str, SOVItem] = {}
self.applications: List[PaymentApplication] = []
self.change_orders_total: float = 0
def setup_sov(self, items: List[Dict[str, Any]]):
"""Initialize Schedule of Values."""
for item in items:
sov = SOVItem(
item_number=item['number'],
description=item['description'],
scheduled_value=item['value'],
work_completed_previous=0,
work_completed_current=0,
materials_stored_previous=0,
materials_stored_current=0,
total_completed_previous=0
)
self.sov_items[item['number']] = sov
def add_change_order(self, amount: float, description: str, item_number: str = None):
"""Add approved change order to contract."""
self.change_orders_total += amount
if item_number:
# Add to existing item
if item_number in self.sov_items:
self.sov_items[item_number].scheduled_value += amount
else:
# Create new line item
new_number = f"CO-{len([i for i in self.sov_items if 'CO' in i]) + 1:02d}"
self.sov_items[new_number] = SOVItem(
item_number=new_number,
description=f"Change Order: {description}",
scheduled_value=amount,
work_completed_previous=0,
work_completed_current=0,
materials_stored_previous=0,
materials_stored_current=0,
total_completed_previous=0
)
def create_application(self, period_from: date, period_to: date,
progress: Dict[str, Dict[str, float]]) -> PaymentApplication:
"""Create new payment application."""
app_number = len(self.applications) + 1
# Update progress for each item
items_copy = []
for item_num, sov in self.sov_items.items():
# Carry forward previous values
updated_sov = SOVItem(
item_number=sov.item_number,
description=sov.description,
scheduled_value=sov.scheduled_value,
work_completed_previous=sov.total_completed_current - sov.materials_stored_current,
work_completed_current=0,
materials_stored_previous=sov.materials_stored_current,
materials_stored_current=0,
total_completed_previous=sov.total_completed_current
)
# Apply current period progress
if item_num in progress:
prog = progress[item_num]
if 'work' in prog:
updated_sov.work_completed_current = prog['work']
if 'materials' in prog:
updated_sov.materials_stored_current = prog['materials']
items_copy.append(updated_sov)
# Update master SOV
self.sov_items[item_num] = SOVItem(
item_number=updated_sov.item_number,
description=updated_sov.description,
scheduled_value=updated_sov.scheduled_value,
work_completed_previous=updated_sov.work_completed_previous + updated_sov.work_completed_current,
work_completed_current=0,
materials_stored_previous=updated_sov.materials_stored_previous + updated_sov.materials_stored_current,
materials_stored_current=0,
total_completed_previous=updated_sov.total_completed_current
)
application = PaymentApplication(
application_number=app_number,
period_from=period_from,
period_to=period_to,
project_name=self.project_name,
contractor=self.contractor,
owner=self.owner,
contract_sum=self.original_contract,
change_orders_amount=self.change_orders_total,
retainage_percent=self.retainage_percent,
items=items_copy
)
self.applications.append(application)
return application
def calculate_payment_due(self, application: PaymentApplication,
previous_payments: float = None) -> Dict[str, float]:
"""Calculate payment due for application."""
if previous_payments is None:
# Calculate from previous applications
previous_payments = sum(
app.total_earned_less_retainage
for app in self.applications[:-1]
)
current_payment = application.total_earned_less_retainage - previous_payments
return {
'total_completed_to_date': application.total_completed_to_date,
'retainage_held': application.retainage_amount,
'total_earned_less_retainage': application.total_earned_less_retainage,
'previous_payments': previous_payments,
'current_payment_due': current_payment,
'balance_to_finish': application.balance_to_finish,
'percent_complete': round(
application.total_completed_to_date / application.total_contract_sum * 100, 1
) if application.total_contract_sum > 0 else 0
}
def generate_g702(self, application: PaymentApplication) -> Dict[str, Any]:
"""Generate AIA G702 Application summary."""
payment = self.calculate_payment_due(application)
return {
'document': 'AIA Document G702',
'application_number': application.application_number,
'period_to': application.period_to.isoformat(),
'project': application.project_name,
'contractor': application.contractor,
'owner': application.owner,
'original_contract_sum': application.contract_sum,
'net_change_orders': application.change_orders_amount,
'contract_sum_to_date': application.total_contract_sum,
'total_completed_to_date': payment['total_completed_to_date'],
'retainage': {
'percent': application.retainage_percent * 100,
'amount': payment['retainage_held']
},
'total_earned_less_retainage': payment['total_earned_less_retainage'],
'previous_certificates': payment['previous_payments'],
'current_payment_due': payment['current_payment_due'],
'balance_to_finish': payment['balance_to_finish']
}
def generate_g703(self, application: PaymentApplication) -> pd.DataFrame:
"""Generate AIA G703 Continuation Sheet."""
data = []
for item in application.items:
data.append({
'Item No.': item.item_number,
'Description': item.description,
'Scheduled Value': item.scheduled_value,
'Work Completed - Previous': item.work_completed_previous,
'Work Completed - This Period': item.work_completed_current,
'Materials Stored - Previous': item.materials_stored_previous,
'Materials Stored - This Period': item.materials_stored_current,
'Total Completed & Stored': item.total_completed_current,
'% Complete': round(item.percent_complete, 1),
'Balance to Finish': item.balance_to_finish,
'Retainage': item.total_completed_current * application.retainage_percent
})
# Add totals row
df = pd.DataFrame(data)
totals = df.select_dtypes(include='number').sum()
totals['Item No.'] = ''
totals['Description'] = 'TOTALS'
totals['% Complete'] = round(
application.total_completed_to_date / application.total_contract_sum * 100, 1
) if application.total_contract_sum > 0 else 0
df = pd.concat([df, pd.DataFrame([totals])], ignore_index=True)
return df
def export_application(self, application: PaymentApplication, output_path: str):
"""Export payment application to Excel."""
with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
# G702 Summary
g702 = self.generate_g702(application)
g702_df = pd.DataFrame([{'Field': k, 'Value': v} for k, v in g702.items()
if not isinstance(v, dict)])
g702_df.to_excel(writer, sheet_name='G702 Summary', index=False)
# G703 Continuation
g703 = self.generate_g703(application)
g703.to_excel(writer, sheet_name='G703 Continuation', index=False)
return output_pathQuick Start
from datetime import date
# Initialize generator
generator = PaymentApplicationGenerator(
project_name="Office Tower",
contractor="ABC Construction",
owner="XYZ Development",
original_contract=10000000,
retainage=0.10
)
# Setup Schedule of Values
generator.setup_sov([
{'number': '01', 'description': 'General Conditions', 'value': 500000},
{'number': '02', 'description': 'Site Work', 'value': 800000},
{'number': '03', 'description': 'Concrete', 'value': 2000000},
])
# Create application with progress
app = generator.create_application(
period_from=date(2024, 1, 1),
period_to=date(2024, 1, 31),
progress={
'01': {'work': 50000},
'02': {'work': 200000, 'materials': 50000},
'03': {'work': 100000}
}
)
# Calculate payment
payment = generator.calculate_payment_due(app)
print(f"Current Payment Due: ${payment['current_payment_due']:,.2f}")Common Use Cases
1. Generate G702/G703
g702 = generator.generate_g702(app)
g703 = generator.generate_g703(app)2. Export Application
generator.export_application(app, "pay_app_001.xlsx")3. Add Change Order
generator.add_change_order(150000, "Additional MEP work", item_number='03')Resources
- DDC Book: Chapter 3.1 - Cost Management
- Reference: AIA Documents G702, G703