build accounting software

I need to build an accounting software that will be integrated to HMRC VAT online submission, Annual account submission as well as Payroll system. The software should be able to produce invoices and send the invoices to the clients via email, the software should have the following capability: Automatic calculation of VAT on mileage Self Assessment calculation and optional submission Automatic corporation tax estimates IR35 deemed salary report Automatic dividend vouchers Multi-line journal entries Trial balance Flexible reporting, including P&L, balance sheet, aged debtors/creditors and trial balance Upcoming tax liabilities and deadlines displayed on the Tax Timeline Fully integrated HMRC-compliant bulk payroll including RTI submission At-a-glance overview of your clients’ businesses Automatic unlimited bank feeds and transactions Easy tracking of out-of-pocket expenses Multi-currency invoices, expenses, and bank accounts Practice dashboard for drill down to the account of any of my clients Cloud based with capability to assign login to client to post and view their specific platform only