The verdict in three sentences
Beyond 500 units, spreadsheets become a financial risk for a London lettings agency: payout errors, arrears spotted too late and landlords calling to ask where their money is. Custom property management software costs between 30,000 and 80,000 GBP in 2026 for a 3 to 5 month project, with a landlord portal, automatic rent statements and staged arrears reminders. For 900 units, the investment usually pays back in 18 to 30 months through recovered accounting time and lower arrears.
What spreadsheet management really costs at 900 units
A mid-sized agency managing flats and offices across Zone 1 and Zone 2 collects several hundred rents every month, mostly by bank transfer and standing order. The workbook holds as long as one person masters it. When that person is on holiday, landlord payouts slip and complaints follow.
| Monthly task (900 units) | On spreadsheets | With dedicated software |
|---|---|---|
| Rent, service charge and fee calculation | 5 to 6 days | 0.5 day (review) |
| Rent statements and receipts | 2 days | Automatic |
| Landlord statements and payouts | 3 days | 0.5 day |
| Time to detect a missed rent | 15 to 30 days | Day 1 |
| Arrears rate (order of magnitude) | 4 to 6% | 2 to 3% |
| Landlord calls per month | 150 to 250 | 40 to 70 |
| Payout errors per quarter | 10 to 20 | Fewer than 2 |
These 2026 orders of magnitude come from typical property management projects. They vary with the share of commercial units, tenancy quality and data discipline, but the trend is constant: freed time is counted in weeks per month.
Features and budget: what to price
Useful property management software for a London agency covers four blocks: units and tenancies (rent reviews, deposit protection deadlines, renewals), client money accounting with payouts, landlord and tenant relations, and arrears tracking with staged reminders by SMS, email then letter.
| Module | 2026 market budget (GBP, ex VAT) | Timeline |
|---|---|---|
| Units, tenancies, rent reviews | 7,000 to 15,000 | 4 to 6 weeks |
| Automatic rent demands and receipts | 3,500 to 8,000 | 2 to 3 weeks |
| Client money accounting and payouts | 8,000 to 20,000 | 5 to 7 weeks |
| Landlord web and mobile portal | 5,000 to 14,000 | 3 to 5 weeks |
| Arrears tracking and SMS reminders | 3,500 to 10,000 | 2 to 4 weeks |
| Maintenance tickets and contractors | 3,000 to 13,000 | 2 to 4 weeks |
| Typical total project | 30,000 to 80,000 | 3 to 5 months |
Add maintenance of roughly 350 to 1,000 GBP per month depending on service level (hosting, backups, fixes, small changes). Off-the-shelf SaaS tools exist, often billed 1 to 3 GBP per unit per month, but they struggle with agency-specific workflows: block management, mixed residential and commercial portfolios, overseas landlords paid in several currencies.
Compliance points
UK GDPR requires securing tenant data (ID documents, bank details, right-to-rent checks). Client money must be ring-fenced and reconciled, and agencies must belong to a Client Money Protection scheme. Serious software provides role-based access, a full audit log and documented hosting.
Mini case study
Sophie, managing director of a lettings agency in Clapham, runs 900 units with three accounts staff. Illustrative scenario: the project costs 55,000 GBP and maintenance 700 GBP a month, i.e. 63,400 GBP in year one.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Estimated annual gains: 8 accounting days freed per month at 220 GBP per day, i.e. 21,120 GBP a year. Arrears drop from 5% to 3% on an average rent of 2,000 GBP: 900 x 2,000 x 12 x 2% = 432,000 GBP better collected, on which the agency earns a 10% management fee, about 43,200 GBP. Total: roughly 64,000 GBP a year, payback in about 12 months.
FAQ
How much does custom property management software cost in London in 2026?
Budget 30,000 to 80,000 GBP ex VAT for a full scope (tenancies, rent demands, client money, landlord portal, arrears). A first phase limited to statements and payouts can start around 18,000 GBP.
How long does it take to move off spreadsheets?
Between 3 and 5 months, including 3 to 4 weeks of data migration. Migrating 900 units is done by controlled import, with one month of parallel running.
Should we choose SaaS over custom software?
A SaaS at 1 to 3 GBP per unit per month suits portfolios under 300 standard tenancies. Above that, or with many commercial units, custom software usually pays off in 2 to 3 years.
Can overseas landlords track their income?
Yes, the portal shows rents collected, charges, fees and payouts in real time, with PDF statements. Agencies typically see inbound calls fall by 60 to 70%.
What does maintenance cost?
Between 350 and 1,000 GBP per month depending on hosting, backups and planned change volume.
Let's scope your project. Send us your unit count, collection methods and payout rules: we will price a scope, an indicative GBP budget and a phased schedule. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
